Exam-Style Problems

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June 2023 p32 q6
1809

The equation \(\cot \frac{1}{2}x = 3x\) has one root in the interval \(0 < x < \pi\), denoted by \(\alpha\).

(a) Show by calculation that \(\alpha\) lies between 0.5 and 1.

(b) Show that, if a sequence of positive values given by the iterative formula \(x_{n+1} = \frac{1}{3} \left( x_n + 4 \arctan \left( \frac{1}{3x_n} \right) \right)\) converges, then it converges to \(\alpha\).

(c) Use this iterative formula to calculate \(\alpha\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2014 p33 q4
1810

The equation \(x = \frac{10}{e^{2x} - 1}\) has one positive real root, denoted by \(\alpha\).

  1. Show that \(\alpha\) lies between \(x = 1\) and \(x = 2\).
  2. Show that if a sequence of positive values given by the iterative formula \(x_{n+1} = \frac{1}{2} \ln \left( 1 + \frac{10}{x_n} \right)\) converges, then it converges to \(\alpha\).
  3. Use this iterative formula to determine \(\alpha\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
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June 2013 p32 q2
1811

The sequence of values given by the iterative formula

\(x_{n+1} = \frac{x_n(x_n^3 + 100)}{2(x_n^3 + 25)}\),

with initial value \(x_1 = 3.5\), converges to \(\alpha\).

  1. Use this formula to calculate \(\alpha\) correct to 4 decimal places, showing the result of each iteration to 6 decimal places.
  2. State an equation satisfied by \(\alpha\) and hence find the exact value of \(\alpha\).
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Nov 2012 p33 q6
1812

The diagram shows the curve \(y = x^4 + 2x^3 + 2x^2 - 4x - 16\), which crosses the x-axis at the points \((\alpha, 0)\) and \((\beta, 0)\) where \(\alpha < \beta\). It is given that \(\alpha\) is an integer.

  1. Find the value of \(\alpha\).
  2. Show that \(\beta\) satisfies the equation \(x = \sqrt[3]{8 - 2x}\).
  3. Use an iteration process based on the equation in part (ii) to find the value of \(\beta\) correct to 2 decimal places. Show the result of each iteration to 4 decimal places.
problem image 1812
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June 2012 p31 q10
1813

(i) It is given that \(2 \tan 2x + 5 \tan^2 x = 0\). Denoting \(\tan x\) by \(t\), form an equation in \(t\) and hence show that either \(t = 0\) or \(t = \sqrt[3]{(t + 0.8)}\).

(ii) It is given that there is exactly one real value of \(t\) satisfying the equation \(t = \sqrt[3]{(t + 0.8)}\). Verify by calculation that this value lies between 1.2 and 1.3.

(iii) Use the iterative formula \(t_{n+1} = \sqrt[3]{(t_n + 0.8)}\) to find the value of \(t\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

(iv) Using the values of \(t\) found in previous parts of the question, solve the equation \(2 \tan 2x + 5 \tan^2 x = 0\) for \(-\pi \leq x \leq \pi\).

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Nov 2009 p32 q2
1814

The equation \(x^3 - 8x - 13 = 0\) has one real root.

(i) Find the two consecutive integers between which this root lies.

(ii) Use the iterative formula \(x_{n+1} = (8x_n + 13)^{\frac{1}{3}}\) to determine this root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2009 p31 q3
1815

The sequence of values given by the iterative formula \(x_{n+1} = \frac{3x_n}{4} + \frac{15}{x_n^3}\), with initial value \(x_1 = 3\), converges to \(\alpha\).

(i) Use this iterative formula to find \(\alpha\) correct to 2 decimal places, giving the result of each iteration to 4 decimal places.

(ii) State an equation satisfied by \(\alpha\) and hence find the exact value of \(\alpha\).

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June 2009 p3 q4
1816

The equation \(x^3 - 2x - 2 = 0\) has one real root.

(i) Show by calculation that this root lies between \(x = 1\) and \(x = 2\).

(ii) Prove that, if a sequence of values given by the iterative formula \(x_{n+1} = \frac{2x_n^3 + 2}{3x_n^2 - 2}\) converges, then it converges to this root.

(iii) Use this iterative formula to calculate the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2005 p3 q4
1817

The equation \(x^3 - x - 3 = 0\) has one real root, \(\alpha\).

(i) Show that \(\alpha\) lies between 1 and 2.

Two iterative formulae derived from this equation are as follows:

\(x_{n+1} = x_n^3 - 3, \quad (A)\)

\(x_{n+1} = (x_n + 3)^{\frac{1}{3}}, \quad (B)\)

Each formula is used with initial value \(x_1 = 1.5\).

(ii) Show that one of these formulae produces a sequence which fails to converge, and use the other formula to calculate \(\alpha\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2004 p3 q7
1818

(i) The equation \(x^3 + x + 1 = 0\) has one real root. Show by calculation that this root lies between \(-1\) and \(0\).

(ii) Show that, if a sequence of values given by the iterative formula \(x_{n+1} = \frac{2x_n^3 - 1}{3x_n^2 + 1}\) converges, then it converges to the root of the equation given in part (i).

(iii) Use this iterative formula, with initial value \(x_1 = -0.5\), to determine the root correct to 2 decimal places, showing the result of each iteration.

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June 2002 p3 q4
1819

The sequence of values given by the iterative formula \(x_{n+1} = \frac{2}{3} \left( x_n + \frac{1}{x_n^2} \right)\), with initial value \(x_1 = 1\), converges to \(\alpha\).

(i) Use this formula to find \(\alpha\) correct to 2 decimal places, showing the result of each iteration.

(ii) State an equation satisfied by \(\alpha\), and hence find the exact value of \(\alpha\).

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June 2020 p32 q9
1820

The diagram shows the curves \(y = \cos x\) and \(y = \frac{k}{1+x}\), where \(k\) is a constant, for \(0 \leq x \leq \frac{1}{2}\pi\). The curves touch at the point where \(x = p\).

(a) Show that \(p\) satisfies the equation \(\tan p = \frac{1}{1+p}\).

(b) Use the iterative formula \(p_{n+1} = \arctan\left(\frac{1}{1+p_n}\right)\) to determine the value of \(p\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

(c) Hence find the value of \(k\) correct to 2 decimal places.

problem image 1820
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June 2019 p33 q6
1821

The diagram shows the curve \(y = x^4 - 2x^3 - 7x - 6\). The curve intersects the \(x\)-axis at the points \((a, 0)\) and \((b, 0)\), where \(a < b\). It is given that \(b\) is an integer.

  1. Find the value of \(b\).
  2. Hence show that \(a\) satisfies the equation \(a = -\frac{1}{3}(2 + a^2 + a^3)\).
  3. Use an iterative formula based on the equation in part (ii) to determine \(a\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.
problem image 1821
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Feb/Mar 2019 p32 q2
1822

The sequence of values given by the iterative formula

\(x_{n+1} = \frac{2x_n^6 + 12x_n}{3x_n^5 + 8}\),

with initial value \(x_1 = 2\), converges to \(\alpha\).

(i) Use the formula to calculate \(\alpha\) correct to 4 decimal places. Give the result of each iteration to 6 decimal places. [3]

(ii) State an equation satisfied by \(\alpha\) and hence find the exact value of \(\alpha\). [2]

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Nov 2017 p31 q3
1823

The equation \(x^3 = 3x + 7\) has one real root, denoted by \(\alpha\).

(i) Show by calculation that \(\alpha\) lies between 2 and 3.

Two iterative formulae, \(A\) and \(B\), derived from this equation are as follows:

\(x_{n+1} = (3x_n + 7)^{\frac{1}{3}}\), \quad (A)

\(x_{n+1} = \frac{x_n^3 - 7}{3}\). \quad (B)

Each formula is used with initial value \(x_1 = 2.5\).

(ii) Show that one of these formulae produces a sequence which fails to converge, and use the other formula to calculate \(\alpha\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2017 p33 q6
1824

The equation \(\cot x = 1 - x\) has one root in the interval \(0 < x < \pi\), denoted by \(\alpha\).

(i) Show by calculation that \(\alpha\) is greater than 2.5.

(ii) Show that, if a sequence of values in the interval \(0 < x < \pi\) given by the iterative formula \(x_{n+1} = \pi + \arctan \left( \frac{1}{1-x_n} \right)\) converges, then it converges to \(\alpha\).

(iii) Use this iterative formula to determine \(\alpha\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

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Nov 2016 p33 q9
1825

The diagram shows the curves \(y = x \cos x\) and \(y = \frac{k}{x}\), where \(k\) is a constant, for \(0 < x \leq \frac{1}{2} \pi\). The curves touch at the point where \(x = a\).

  1. Show that \(a\) satisfies the equation \(\tan a = \frac{2}{a}\).
  2. Use the iterative formula \(a_{n+1} = \arctan \left( \frac{2}{a_n} \right)\) to determine \(a\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.
  3. Hence find the value of \(k\) correct to 2 decimal places.
problem image 1825
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Feb/Mar 2016 p32 q3
1826

The equation \(x^5 - 3x^3 + x^2 - 4 = 0\) has one positive root.

  1. Verify by calculation that this root lies between 1 and 2. [2]
  2. Show that the equation can be rearranged in the form \(x = \sqrt[3]{3x + \frac{4}{x^2} - 1}\). [1]
  3. Use an iterative formula based on this rearrangement to determine the positive root correct to 2 decimal places. Give the result of each iteration to 4 decimal places. [3]
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Nov 2015 p31 q4
1827

The equation \(x^3 - x^2 - 6 = 0\) has one real root, denoted by \(\alpha\).

(i) Find by calculation the pair of consecutive integers between which \(\alpha\) lies.

(ii) Show that, if a sequence of values given by the iterative formula \(x_{n+1} = \sqrt{x_n + \frac{6}{x_n}}\) converges, then it converges to \(\alpha\).

(iii) Use this iterative formula to determine \(\alpha\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

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June 2023 p33 q5
1828

The diagram shows the part of the curve \(y = x^2 \cos 3x\) for \(0 \leq x \leq \frac{1}{6}\pi\), and its maximum point \(M\), where \(x = a\).

(a) Show that \(a\) satisfies the equation \(a = \frac{1}{3} \arctan \left( \frac{2}{3a} \right)\).

(b) Use an iterative formula based on the equation in (a) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1828
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Nov 2018 p32 q5
1829

The equation of a curve is \(y = x \ln(8 - x)\). The gradient of the curve is equal to 1 at only one point, when \(x = a\).

(i) Show that \(a\) satisfies the equation \(x = 8 - \frac{8}{\ln(8 - x)}\).

(ii) Verify by calculation that \(a\) lies between 2.9 and 3.1.

(iii) Use an iterative formula based on the equation in part (i) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2016 p33 q6
1830

The curve with equation \(y = x^2 \cos \frac{1}{2}x\) has a stationary point at \(x = p\) in the interval \(0 < x < \pi\).

  1. Show that \(p\) satisfies the equation \(\tan \frac{1}{2}p = \frac{4}{p}\).
  2. Verify by calculation that \(p\) lies between 2 and 2.5.
  3. Use the iterative formula \(p_{n+1} = 2 \arctan \left( \frac{4}{p_n} \right)\) to determine the value of \(p\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
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June 2016 p32 q8
1831

The diagram shows the curve \(y = \csc x\) for \(0 < x < \pi\) and part of the curve \(y = e^{-x}\). When \(x = a\), the tangents to the curves are parallel.

(i) By differentiating \(\frac{1}{\sin x}\), show that if \(y = \csc x\) then \(\frac{dy}{dx} = -\csc x \cot x\). [3]

(ii) By equating the gradients of the curves at \(x = a\), show that \(a = \arctan \left( \frac{e^a}{\sin a} \right)\). [2]

(iii) Verify by calculation that \(a\) lies between 1 and 1.5. [2]

(iv) Use an iterative formula based on the equation in part (ii) to determine \(a\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places. [3]

problem image 1831
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Nov 2015 p33 q4
1832

A curve has parametric equations

\(x = t^2 + 3t + 1, \quad y = t^4 + 1.\)

The point \(P\) on the curve has parameter \(p\). It is given that the gradient of the curve at \(P\) is 4.

  1. Show that \(p = \sqrt[3]{2p + 3}\).
  2. Verify by calculation that the value of \(p\) lies between 1.8 and 2.0.
  3. Use an iterative formula based on the equation in part (i) to find the value of \(p\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
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June 2015 p31 q10
1833

The diagram shows part of the curve with parametric equations

\(x = 2 \ln(t + 2)\), \(y = t^3 + 2t + 3\).

  1. Find the gradient of the curve at the origin. [5]
  2. At the point \(P\) on the curve, the value of the parameter is \(p\). It is given that the gradient of the curve at \(P\) is \(\frac{1}{2}\).
    1. Show that \(p = \frac{1}{3p^2 + 2} - 2\). [1]
    2. By first using an iterative formula based on the equation in part (a), determine the coordinates of the point \(P\). Give the result of each iteration to 5 decimal places and each coordinate of \(P\) correct to 2 decimal places. [4]
problem image 1833
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June 2013 p33 q6
1834

The diagram shows the curves \(y = e^{2x-3}\) and \(y = 2 \ln x\). When \(x = a\) the tangents to the curves are parallel.

  1. Show that \(a\) satisfies the equation \(a = \frac{1}{2}(3 - \ln a)\). [3]
  2. Verify by calculation that this equation has a root between 1 and 2. [2]
  3. Use the iterative formula \(a_{n+1} = \frac{1}{2}(3 - \ln a_n)\) to calculate \(a\) correct to 2 decimal places, showing the result of each iteration to 4 decimal places. [3]
problem image 1834
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Nov 2012 p31 q8
1835

The diagram shows the curve \(y = e^{-\frac{1}{2}x^2} \sqrt{(1 + 2x^2)}\) for \(x \geq 0\), and its maximum point \(M\).

(i) Find the exact value of the \(x\)-coordinate of \(M\). [4]

(ii) The sequence of values given by the iterative formula \(x_{n+1} = \sqrt{(\ln(4 + 8x_n^2))}\), with initial value \(x_1 = 2\), converges to a certain value \(\alpha\). State an equation satisfied by \(\alpha\) and hence show that \(\alpha\) is the \(x\)-coordinate of a point on the curve where \(y = 0.5\). [3]

(iii) Use the iterative formula to determine \(\alpha\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places. [3]

problem image 1835
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June 2010 p33 q6
1836

The curve \(y = \frac{\ln x}{x + 1}\) has one stationary point.

(i) Show that the \(x\)-coordinate of this point satisfies the equation \(x = \frac{x + 1}{\ln x}\), and that this \(x\)-coordinate lies between 3 and 4.

(ii) Use the iterative formula \(x_{n+1} = \frac{x_n + 1}{\ln x_n}\) to determine the \(x\)-coordinate correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2010 p32 q4
1837

The diagram shows the curve \(y = \frac{\sin x}{x}\) for \(0 < x \leq 2\pi\), and its minimum point \(M\).

(i) Show that the \(x\)-coordinate of \(M\) satisfies the equation \(x = \tan x\).

(ii) The iterative formula \(x_{n+1} = \arctan(x_n) + \pi\) can be used to determine the \(x\)-coordinate of \(M\). Use this formula to determine the \(x\)-coordinate of \(M\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1837
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June 2003 p3 q8
1838

The equation of a curve is \(y = \ln x + \frac{2}{x}\), where \(x > 0\).

(i) Find the coordinates of the stationary point of the curve and determine whether it is a maximum or a minimum point.

(ii) The sequence of values given by the iterative formula \(x_{n+1} = \frac{2}{3 - \ln x_n}\), with initial value \(x_1 = 1\), converges to \(\alpha\). State an equation satisfied by \(\alpha\), and hence show that \(\alpha\) is the \(x\)-coordinate of a point on the curve where \(y = 3\).

(iii) Use this iterative formula to find \(\alpha\) correct to 2 decimal places, showing the result of each iteration.

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Nov 2022 p33 q8
1839

The curve with equation \(y = \frac{x^3}{e^x - 1}\) has a stationary point at \(x = p\), where \(p > 0\).

(a) Show that \(p = 3(1 - e^{-p})\).

(b) Verify by calculation that \(p\) lies between 2.5 and 3.

(c) Use an iterative formula based on the equation in part (a) to determine \(p\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2022 p31 q7
1840

The equation of a curve is \(y = \frac{x}{\cos^2 x}\), for \(0 \leq x < \frac{1}{2}\pi\). At the point where \(x = a\), the tangent to the curve has gradient equal to 12.

(a) Show that \(a = \cos^{-1} \left( \sqrt[3]{\frac{\cos a + 2a \sin a}{12}} \right)\).

(b) Verify by calculation that \(a\) lies between 0.9 and 1.

(c) Use an iterative formula based on the equation in part (a) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2022 p31 q10
1841

The curve \(y = x \sqrt{\sin x}\) has one stationary point in the interval \(0 < x < \pi\), where \(x = a\) (see diagram).

(a) Show that \(\tan a = -\frac{1}{2}a\).

(b) Verify by calculation that \(a\) lies between 2 and 2.5.

(c) Show that if a sequence of values in the interval \(0 < x < \pi\) given by the iterative formula \(x_{n+1} = \pi - \arctan\left(\frac{1}{2}x_n\right)\) converges, then it converges to \(a\), the root of the equation in part (a).

(d) Use the iterative formula given in part (c) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1841
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Nov 2021 p32 q11
1842

The equation of a curve is \(y = \sqrt{\tan x}\), for \(0 \leq x < \frac{1}{2}\pi\).

(a) Express \(\frac{dy}{dx}\) in terms of \(\tan x\), and verify that \(\frac{dy}{dx} = 1\) when \(x = \frac{1}{4}\pi\).

The value of \(\frac{dy}{dx}\) is also 1 at another point on the curve where \(x = a\), as shown in the diagram.

(b) Show that \(t^3 + t^2 + 3t - 1 = 0\), where \(t = \tan a\).

(c) Use the iterative formula \(a_{n+1} = \arctan \left( \frac{1}{3} (1 - \tan^2 a_n - \tan^3 a_n) \right)\) to determine \(a\) correct to 2 decimal places, giving the result of each iteration to 4 decimal places.

problem image 1842
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June 2021 p31 q7
1843

The diagram shows the curve \(y = \frac{\arctan x}{\sqrt{x}}\) and its maximum point \(M\) where \(x = a\).

(a) Show that \(a\) satisfies the equation \(a = \tan \left( \frac{2a}{1 + a^2} \right)\).

(b) Verify by calculation that \(a\) lies between 1.3 and 1.5.

(c) Use an iterative formula based on the equation in part (a) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1843
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Feb/Mar 2021 p32 q9
1844

Let \(f(x) = \frac{e^{2x} + 1}{e^{2x} - 1}\), for \(x > 0\).

(a) The equation \(x = f(x)\) has one root, denoted by \(a\). Verify by calculation that \(a\) lies between 1 and 1.5. [2]

(b) Use an iterative formula based on the equation in part (a) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places. [3]

(c) Find \(f'(x)\). Hence find the exact value of \(x\) for which \(f'(x) = -8\). [6]

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Nov 2019 p31 q5
1845

The curve with equation \(y = e^{-2x} \ln(x-1)\) has a stationary point when \(x = p\).

  1. Show that \(p\) satisfies the equation \(x = 1 + \exp\left( \frac{1}{2(x-1)} \right)\), where \(\exp(x)\) denotes \(e^x\).
  2. Verify by calculation that \(p\) lies between 2.2 and 2.6.
  3. Use an iterative formula based on the equation in part (i) to determine \(p\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
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June 2019 p31 q7
1846

The diagram shows the curves \(y = 4 \, \cos \frac{1}{2} x\) and \(y = \frac{1}{4-x}\), for \(0 \leq x < 4\). When \(x = a\), the tangents to the curves are perpendicular.

  1. Show that \(a = 4 - \sqrt{2 \sin \frac{1}{2} a}\).
  2. Verify by calculation that \(a\) lies between 2 and 3.
  3. Use an iterative formula based on the equation in part (i) to determine \(a\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.
problem image 1846
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June 2023 p31 q9
1847

The constant a is such that \(\int_0^a xe^{-2x} \, dx = \frac{1}{8}\).

(a) Show that \(a = \frac{1}{2} \ln(4a + 2)\).

(b) Verify by calculation that a lies between 0.5 and 1.

(c) Use an iterative formula based on the equation in (a) to determine a correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2014 p31 q6
1848

It is given that \(\int_{1}^{a} \ln(2x) \, dx = 1\), where \(a > 1\).

(i) Show that \(a = \frac{1}{2} \exp \left( 1 + \frac{\ln 2}{a} \right)\), where \(\exp(x)\) denotes \(e^x\).

(ii) Use the iterative formula \(a_{n+1} = \frac{1}{2} \exp \left( 1 + \frac{\ln 2}{a_n} \right)\) to determine the value of \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2013 p33 q5
1849

It is given that \(\int_0^p 4xe^{-\frac{1}{2}x} \, dx = 9\), where \(p\) is a positive constant.

(i) Show that \(p = 2 \ln \left( \frac{8p + 16}{7} \right)\).

(ii) Use an iterative process based on the equation in part (i) to find the value of \(p\) correct to 3 significant figures. Use a starting value of 3.5 and give the result of each iteration to 5 significant figures.

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June 2012 p33 q7
1850

The diagram shows part of the curve \(y = \\cos(\sqrt{x})\) for \(x \geq 0\), where \(x\) is in radians. The shaded region between the curve, the axes and the line \(x = p^2\), where \(p > 0\), is denoted by \(R\). The area of \(R\) is equal to 1.

(i) Use the substitution \(x = u^2\) to find \(\int_0^{p^2} \cos(\sqrt{x}) \, dx\). Hence show that \(\sin p = \frac{3 - 2 \cos p}{2p}\).

(ii) Use the iterative formula \(p_{n+1} = \sin^{-1} \left( \frac{3 - 2 \cos p_n}{2p_n} \right)\), with initial value \(p_1 = 1\), to find the value of \(p\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1850
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Nov 2011 p33 q5
1851

It is given that \(\int_1^a x \ln x \, dx = 22\), where \(a\) is a constant greater than 1.

(i) Show that \(a = \sqrt{\frac{87}{2 \ln a - 1}}\).

(ii) Use an iterative formula based on the equation in part (i) to find the value of \(a\) correct to 2 decimal places. Use an initial value of 6 and give the result of each iteration to 4 decimal places.

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Nov 2010 p33 q7
1852

(i) Given that \(\int_1^a \frac{\ln x}{x^2} \, dx = \frac{2}{5}\), show that \(a = \frac{5}{3}(1 + \ln a)\).

(ii) Use an iteration formula based on the equation \(a = \frac{5}{3}(1 + \ln a)\) to find the value of \(a\) correct to 2 decimal places. Use an initial value of 4 and give the result of each iteration to 4 decimal places.

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Nov 2006 p3 q10
1853

The diagram shows the curve \(y = x \cos 2x\) for \(0 \leq x \leq \frac{1}{4} \pi\). The point \(M\) is a maximum point.

  1. Show that the \(x\)-coordinate of \(M\) satisfies the equation \(1 = 2x \tan 2x\).
  2. The equation in part (i) can be rearranged in the form \(x = \frac{1}{2} \arctan \left( \frac{1}{2x} \right)\). Use the iterative formula \(x_{n+1} = \frac{1}{2} \arctan \left( \frac{1}{2x_n} \right)\), with initial value \(x_1 = 0.4\), to calculate the \(x\)-coordinate of \(M\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
  3. Use integration by parts to find the exact area of the region enclosed between the curve and the \(x\)-axis from \(0\) to \(\frac{1}{4} \pi\).
problem image 1853
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June 2022 p33 q10
1854

The constant \(a\) is such that \(\int_{1}^{a} x^2 \ln x \, dx = 4\).

(a) Show that \(a = \left( \frac{35}{3 \ln a - 1} \right)^{\frac{1}{3}}\).

(b) Verify by calculation that \(a\) lies between 2.4 and 2.8.

(c) Use an iterative formula based on the equation in part (a) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2021 p31 q8
1855

The constant \(a\) is such that \(\int_1^a \frac{\ln x}{\sqrt{x}} \, dx = 6\).

(a) Show that \(a = \exp \left( \frac{1}{\sqrt{a}} + 2 \right)\).

[\(\exp(x)\) is an alternative notation for \(e^x\).]

(b) Verify by calculation that \(a\) lies between 9 and 11.

(c) Use an iterative formula based on the equation in part (a) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2020 p32 q10
1856

The diagram shows the curve \(y = \sqrt{x} \cos x\), for \(0 \leq x \leq \frac{3}{2}\pi\), and its minimum point \(M\), where \(x = a\). The shaded region between the curve and the x-axis is denoted by \(R\).

(a) Show that \(a\) satisfies the equation \(\tan a = \frac{1}{2a}\).

(b) The sequence of values given by the iterative formula \(a_{n+1} = \pi + \arctan\left(\frac{1}{2a_n}\right)\), with initial value \(x_1 = 3\), converges to \(a\). Use this formula to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

(c) Find the volume of the solid obtained when the region \(R\) is rotated completely about the x-axis. Give your answer in terms of \(\pi\).

problem image 1856
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Nov 2019 p32 q9
1857

It is given that \(\int_0^a x \cos \frac{1}{3}x \, dx = 3\), where the constant \(a\) is such that \(0 < a < \frac{3}{2}\pi\).

(i) Show that \(a\) satisfies the equation \(a = \frac{4 - 3 \cos \frac{1}{3}a}{\sin \frac{1}{3}a}.\)

(ii) Verify by calculation that \(a\) lies between 2.5 and 3.

(iii) Use an iterative formula based on the equation in part (i) to calculate \(a\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

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June 2018 p31 q8
1858

The positive constant \(a\) is such that \(\int_0^a x e^{-\frac{1}{2}x} \, dx = 2\).

(i) Show that \(a\) satisfies the equation \(a = 2 \ln(a + 2)\).

(ii) Verify by calculation that \(a\) lies between 3 and 3.5.

(iii) Use an iteration based on the equation in part (i) to determine \(a\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2017 p32 q9
1859

It is given that \(\int_{1}^{a} x^{-2} \ln x \, dx = 2\), where \(a > 1\).

(i) Show that \(a^{\frac{3}{2}} = \frac{7 + 2a^{\frac{3}{2}}}{3 \ln a}\).

(ii) Show by calculation that \(a\) lies between 2 and 4.

(iii) Use the iterative formula \(a_{n+1} = \left( \frac{7 + 2a_n^{\frac{3}{2}}}{3 \ln a_n} \right)^{\frac{2}{3}}\) to determine \(a\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

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June 2017 p32 q10
1860

The diagram shows the curve \(y = x^2 \cos 2x\) for \(0 \leq x \leq \frac{1}{4}\pi\). The curve has a maximum point at \(M\) where \(x = p\).

(i) Show that \(p\) satisfies the equation \(p = \frac{1}{2} \arctan \left( \frac{1}{p} \right)\).

(ii) Use the iterative formula \(p_{n+1} = \frac{1}{2} \arctan \left( \frac{1}{p_n} \right)\) to determine the value of \(p\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

(iii) Find, showing all necessary working, the exact area of the region bounded by the curve and the \(x\)-axis.

problem image 1860
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June 2015 p33 q6
1861

It is given that \(\int_0^a x \cos x \, dx = 0.5\), where \(0 < a < \frac{1}{2} \pi\).

(i) Show that \(a\) satisfies the equation \(\sin a = \frac{1.5 - \cos a}{a}\).

(ii) Verify by calculation that \(a\) is greater than 1.

(iii) Use the iterative formula \(a_{n+1} = \sin^{-1} \left( \frac{1.5 - \cos a_n}{a_n} \right)\) to determine the value of \(a\) correct to 4 decimal places, giving the result of each iteration to 6 decimal places.

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Problem 1862
1862

The diagram shows a circle with centre O and radius r. The angle of the minor sector AOB of the circle is x radians. The area of the major sector of the circle is 3 times the area of the shaded region.

\((a) Show that x = \frac{3}{4} \sin x + \frac{1}{2} \pi.\)

(b) Show by calculation that the root of the equation in (a) lies between 2 and 2.5.

(c) Use an iterative formula based on the equation in (a) to calculate this root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1862
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Nov 2013 p31 q6
1863

In the diagram, A is a point on the circumference of a circle with centre O and radius r. A circular arc with centre A meets the circumference at B and C. The angle OAB is ฮธ radians. The shaded region is bounded by the circumference of the circle and the arc with centre A joining B and C. The area of the shaded region is equal to half the area of the circle.

(i) Show that \(\cos 2ฮธ = \frac{2 \sin 2ฮธ - ฯ€}{4ฮธ}\).

(ii) Use the iterative formula \(ฮธ_{n+1} = \frac{1}{2} \cos^{-1} \left( \frac{2 \sin 2ฮธ_n - ฯ€}{4ฮธ_n} \right)\), with initial value \(ฮธ_1 = 1\), to determine \(ฮธ\) correct to 2 decimal places, showing the result of each iteration to 4 decimal places.

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June 2012 p32 q2
1864

In the diagram, ABC is a triangle in which angle ABC is a right angle and BC = a. A circular arc, with centre C and radius a, joins B and the point M on AC. The angle ACB is b8 radians. The area of the sector CMB is equal to one third of the area of the triangle ABC.

(i) Show that b8 satisfies the equation

\(\tan \theta = 3\theta\).

(ii) This equation has one root in the interval \(0 < \theta < \frac{1}{2}\pi\). Use the iterative formula

\(\theta_{n+1} = \arctan(3\theta_n)\)

to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2011 p32 q4
1865

The diagram shows a semicircle ACB with centre O and radius r. The tangent at C meets AB produced at T. The angle BOC is x radians. The area of the shaded region is equal to the area of the semicircle.

(i) Show that x satisfies the equation \(\tan x = x + \pi\).

(ii) Use the iterative formula \(x_{n+1} = \arctan(x_n + \pi)\) to determine x correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2011 p31 q6
1866

The diagram shows a circle with centre O and radius 10 cm. The chord AB divides the circle into two regions whose areas are in the ratio 1 : 4 and it is required to find the length of AB. The angle AOB is \(\theta\) radians.

(i) Show that \(\theta = \frac{2}{5}\pi + \sin \theta\).

(ii) Showing all your working, use an iterative formula, based on the equation in part (i), with an initial value of 2.1, to find \(\theta\) correct to 2 decimal places. Hence find the length of AB in centimetres correct to 1 decimal place.

problem image 1866
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June 2010 p31 q6
1867

The diagram shows a semicircle ACB with centre O and radius r. The angle BOC is x radians. The area of the shaded segment is a quarter of the area of the semicircle.

(i) Show that x satisfies the equation

\(x = \frac{3}{4}\pi - \sin x\).

(ii) This equation has one root. Verify by calculation that the root lies between 1.3 and 1.5.

(iii) Use the iterative formula

\(x_{n+1} = \frac{3}{4}\pi - \sin x_n\)

to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1867
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June 2008 p3 q3
1868

In the diagram, ABCD is a rectangle with AB = 3a and AD = a. A circular arc, with centre A and radius r, joins points M and N on AB and CD respectively. The angle MAN is x radians. The perimeter of the sector AMN is equal to half the perimeter of the rectangle.

  1. Show that x satisfies the equation \(\sin x = \frac{1}{4}(2 + x)\).
  2. This equation has only one root in the interval \(0 < x < \frac{1}{2}\pi\). Use the iterative formula \(x_{n+1} = \sin^{-1}\left(\frac{2 + x_n}{4}\right)\), with initial value \(x_1 = 0.8\), to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
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June 2007 p3 q6
1869

The diagram shows a sector AOB of a circle with centre O and radius r. The angle AOB is \(\alpha\) radians, where \(0 < \alpha < \pi\). The area of triangle AOB is half the area of the sector.

  1. Show that \(\alpha\) satisfies the equation \(x = 2 \sin x\).
  2. Verify by calculation that \(\alpha\) lies between \(\frac{1}{2} \pi\) and \(\frac{2}{3} \pi\).
  3. Show that, if a sequence of values given by the iterative formula \(x_{n+1} = \frac{1}{3}(x_n + 4 \sin x_n)\) converges, then it converges to a root of the equation in part (i).
  4. Use this iterative formula, with initial value \(x_1 = 1.8\), to find \(\alpha\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
problem image 1869
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Nov 2002 p3 q7
1870

The diagram shows a curved rod AB of length 100 cm which forms an arc of a circle. The end points A and B of the rod are 99 cm apart. The circle has radius r cm and the arc AB subtends an angle of 2ฮฑ radians at O, the centre of the circle.

(i) Show that ฮฑ satisfies the equation \(\frac{99}{100}x = \sin x\).

(ii) Given that this equation has exactly one root in the interval \(0 < x < \frac{1}{2} \pi\), verify by calculation that this root lies between 0.1 and 0.5.

(iii) Show that if the sequence of values given by the iterative formula \(x_{n+1} = 50 \sin x_n - 48.5 x_n\) converges, then it converges to a root of the equation in part (i).

(iv) Use this iterative formula, with initial value \(x_1 = 0.25\), to find ฮฑ correct to 3 decimal places, showing the result of each iteration.

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Nov 2022 p32 q9
1871

The diagram shows a semicircle with diameter \(AB\), centre \(O\) and radius \(r\). The shaded region is the minor segment on the chord \(AC\) and its area is one third of the area of the semicircle. The angle \(CAB\) is \(\theta\) radians.

(a) Show that \(\theta = \frac{1}{3}(\pi - 1.5 \sin 2\theta)\).

(b) Verify by calculation that \(0.5 < \theta < 0.7\).

(c) Use an iterative formula based on the equation in part (a) to determine \(\theta\) correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

problem image 1871
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June 2021 p32 q10
1872

The diagram shows a trapezium ABCD in which AD = BC = r and AB = 2r. The acute angles BAD and ABC are both equal to x radians. Circular arcs of radius r with centres A and B meet at M, the midpoint of AB.

(a) Given that the sum of the areas of the shaded sectors is 90% of the area of the trapezium, show that x satisfies the equation x = 0.9(2 - \cos x) \sin x.

(b) Verify by calculation that x lies between 0.5 and 0.7.

(c) Show that if a sequence of values in the interval 0 < x < \frac{1}{2}\pi given by the iterative formula \(x_{n+1} = \cos^{-1} \left( \frac{2 - x_n}{0.9 \sin x_n} \right)\) converges, then it converges to the root of the equation in part (a).

(d) Use this iterative formula to determine x correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1872
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June 2020 p31 q6
1873

The diagram shows a circle with centre O and radius r. The tangents to the circle at the points A and B meet at T, and angle AOB is 2x radians. The shaded region is bounded by the tangents AT and BT, and by the minor arc AB. The area of the shaded region is equal to the area of the circle.

(a) Show that x satisfies the equation \(\tan x = \pi + x\).

(b) This equation has one root in the interval \(0 < x < \frac{1}{2}\pi\). Verify by calculation that this root lies between 1 and 1.4.

(c) Use the iterative formula \(x_{n+1} = \arctan(\pi + x_n)\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1873
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June 2019 p32 q6
1874

In the diagram, A is the mid-point of the semicircle with centre O and radius r. A circular arc with centre A meets the semicircle at B and C. The angle OAB is equal to x radians. The area of the shaded region bounded by AB, AC and the arc with centre A is equal to half the area of the semicircle.

  1. Use triangle OAB to show that AB = 2r \cos x. [1]
  2. Hence show that x = \cos^{-1}\left(\sqrt{\frac{\pi}{16x}}\right). [2]
  3. Verify by calculation that x lies between 1 and 1.5. [2]
  4. Use an iterative formula based on the equation in part (ii) to determine x correct to 3 decimal places. Give the result of each iteration to 5 decimal places. [3]
problem image 1874
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Problem 1875
1875

The diagram shows a triangle ABC in which AB = AC = a and angle BAC = \theta radians. Semicircles are drawn outside the triangle with AB and AC as diameters. A circular arc with centre A joins B and C. The area of the shaded segment is equal to the sum of the areas of the semicircles.

  1. Show that \(\theta = \frac{1}{2}\pi + \sin \theta\).
  2. Verify by calculation that \(\theta\) lies between 2.2 and 2.4.
  3. Use an iterative formula based on the equation in part (i) to determine \(\theta\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
problem image 1875
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June 2017 p31 q5
1876

The diagram shows a semicircle with centre O, radius r and diameter AB. The point P on its circumference is such that the area of the minor segment on AP is equal to half the area of the minor segment on BP. The angle AOP is x radians.

  1. Show that x satisfies the equation x = \frac{1}{3}(\pi + \sin x).
  2. Verify by calculation that x lies between 1 and 1.5.
  3. Use an iterative formula based on the equation in part (i) to determine x correct to 3 decimal places. Give the result of each iteration to 5 decimal places.
problem image 1876
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June 2015 p32 q5
1877

The diagram shows a circle with centre O and radius r. The tangents to the circle at the points A and B meet at T, and the angle AOB is 2x radians. The shaded region is bounded by the tangents AT and BT, and by the minor arc AB. The perimeter of the shaded region is equal to the circumference of the circle.

(i) Show that x satisfies the equation \(\tan x = \pi - x\).

(ii) This equation has one root in the interval \(0 < x < \frac{1}{2}\pi\). Verify by calculation that this root lies between 1 and 1.3.

(iii) Use the iterative formula \(x_{n+1} = \arctan(\pi - x_n)\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

problem image 1877
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June 2014 p32 q6
1878

In the diagram, A is a point on the circumference of a circle with centre O and radius r. A circular arc with centre A meets the circumference at B and C. The angle OAB is equal to x radians. The shaded region is bounded by AB, AC and the circular arc with centre A joining B and C. The perimeter of the shaded region is equal to half the circumference of the circle.

  1. Show that \(x = \cos^{-1} \left( \frac{\pi}{4 + 4x} \right)\).
  2. Verify by calculation that x lies between 1 and 1.5.
  3. Use the iterative formula \(x_{n+1} = \cos^{-1} \left( \frac{\pi}{4 + 4x_n} \right)\) to determine the value of x correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
problem image 1878
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Nov 2023 p32 q6
1879

(a) By sketching a suitable pair of graphs, show that the equation \(\cot x = 2 - \cos x\) has one root in the interval \(0 < x \leq \frac{1}{2}\pi\).

(b) Show by calculation that this root lies between 0.6 and 0.8.

(c) Use the iterative formula \(x_{n+1} = \arctan\left( \frac{1}{2 - \cos x_n} \right)\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2018 p31 q3
1880

(i) By sketching a suitable pair of graphs, show that the equation \(x^3 = 3 - x\) has exactly one real root.

(ii) Show that if a sequence of real values given by the iterative formula \(x_{n+1} = \frac{2x_n^3 + 3}{3x_n^2 + 1}\) converges, then it converges to the root of the equation in part (i).

(iii) Use this iterative formula to determine the root correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

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June 2018 p33 q4
1881

The curve with equation \(y = \frac{\ln x}{3 + x}\) has a stationary point at \(x = p\).

  1. Show that \(p\) satisfies the equation \(\ln x = 1 + \frac{3}{x}\).
  2. By sketching suitable graphs, show that the equation in part (i) has only one root.
  3. It is given that the equation in part (i) can be written in the form \(x = \frac{3 + x}{\ln x}\). Use an iterative formula based on this rearrangement to determine the value of \(p\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.
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Problem 1882
1882

(i) By sketching suitable graphs, show that the equation \(e^{2x} = 6 + e^{-x}\) has exactly one real root.

(ii) Verify by calculation that this root lies between 0.5 and 1.

(iii) Show that if a sequence of values given by the iterative formula \(x_{n+1} = \frac{1}{3} \ln(1 + 6e^{x_n})\) converges, then it converges to the root of the equation in part (i).

(iv) Use this iterative formula to calculate the root correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

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Feb/Mar 2017 p32 q3
1883

(i) By sketching suitable graphs, show that the equation \(e^{-\frac{1}{2}x} = 4 - x^2\) has one positive root and one negative root.

(ii) Verify by calculation that the negative root lies between \(-1\) and \(-1.5\).

(iii) Use the iterative formula \(x_{n+1} = -\sqrt{4 - e^{-\frac{1}{2}x_n}}\) to determine this root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2016 p31 q6
1884

(i) By sketching a suitable pair of graphs, show that the equation \(\csc \frac{1}{2}x = \frac{1}{3}x + 1\) has one root in the interval \(0 < x \leq \pi\).

(ii) Show by calculation that this root lies between 1.4 and 1.6.

(iii) Show that, if a sequence of values in the interval \(0 < x \leq \pi\) given by the iterative formula \(x_{n+1} = 2 \sin^{-1} \left( \frac{3}{x_n + 3} \right)\) converges, then it converges to the root of the equation in part (i).

(iv) Use this iterative formula to calculate the root correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

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June 2016 p31 q6
1885

(i) By sketching a suitable pair of graphs, show that the equation \(5e^{-x} = \sqrt{x}\) has one root.

(ii) Show that, if a sequence of values given by the iterative formula \(x_{n+1} = \frac{1}{2} \ln\left(\frac{25}{x_n}\right)\) converges, then it converges to the root of the equation in part (i).

(iii) Use this iterative formula, with initial value \(x_1 = 1\), to calculate the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2014 p33 q9
1886

(i) Sketch the curve \(y = \ln(x + 1)\) and hence, by sketching a second curve, show that the equation \(x^3 + \ln(x + 1) = 40\) has exactly one real root. State the equation of the second curve.

(ii) Verify by calculation that the root lies between 3 and 4.

(iii) Use the iterative formula \(x_{n+1} = \sqrt[3]{40 - \ln(x_n + 1)}\), with a suitable starting value, to find the root correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

(iv) Deduce the root of the equation \((e^y - 1)^3 + y = 40\), giving the answer correct to 2 decimal places.

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June 2014 p31 q8
1887

(i) By sketching each of the graphs \(y = \csc x\) and \(y = x(\pi - x)\) for \(0 < x < \pi\), show that the equation \(\csc x = x(\pi - x)\) has exactly two real roots in the interval \(0 < x < \pi\).

(ii) Show that the equation \(\csc x = x(\pi - x)\) can be written in the form \(x = \frac{1 + x^2 \sin x}{\pi \sin x}\).

(iii) The two real roots of the equation \(\csc x = x(\pi - x)\) in the interval \(0 < x < \pi\) are denoted by \(\alpha\) and \(\beta\), where \(\alpha < \beta\).

(a) Use the iterative formula \(x_{n+1} = \frac{1 + x_n^2 \sin x_n}{\pi \sin x_n}\) to find \(\alpha\) correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

(b) Deduce the value of \(\beta\) correct to 2 decimal places.

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Nov 2011 p31 q5
1888

(i) By sketching a suitable pair of graphs, show that the equation \(\sec x = 3 - \frac{1}{2}x^2\), where \(x\) is in radians, has a root in the interval \(0 < x < \frac{1}{2}\pi\).

(ii) Verify by calculation that this root lies between 1 and 1.4.

(iii) Show that this root also satisfies the equation \(x = \cos^{-1}\left( \frac{2}{6 - x^2} \right)\).

(iv) Use an iterative formula based on the equation in part (iii) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2011 p33 q6
1889

(i) By sketching a suitable pair of graphs, show that the equation \(\cot x = 1 + x^2\), where \(x\) is in radians, has only one root in the interval \(0 < x < \frac{1}{2}\pi\).

(ii) Verify by calculation that this root lies between 0.5 and 0.8.

(iii) Use the iterative formula \(x_{n+1} = \arctan\left( \frac{1}{1 + x_n^2} \right)\) to determine this root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2023 p31 q8
1890

(a) By sketching a suitable pair of graphs, show that the equation \(\sqrt{x} = e^x - 3\) has only one root.

(b) Show by calculation that this root lies between 1 and 2.

(c) Show that, if a sequence of values given by the iterative formula \(x_{n+1} = \ln(3 + \sqrt{x_n})\) converges, then it converges to the root of the equation in (a).

(d) Use the iterative formula to calculate the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2010 p31 q4
1891

(i) By sketching suitable graphs, show that the equation \(4x^2 - 1 = \cot x\) has only one root in the interval \(0 < x < \frac{1}{2}\pi\).

(ii) Verify by calculation that this root lies between 0.6 and 1.

(iii) Use the iterative formula \(x_{n+1} = \frac{1}{2}\sqrt{1 + \cot x_n}\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2008 p3 q9
1892

The constant a is such that \(\int_{0}^{a} xe^{\frac{1}{2}x} \, dx = 6\).

(i) Show that a satisfies the equation \(x = 2 + e^{-\frac{1}{2}x}\).

(ii) By sketching a suitable pair of graphs, show that this equation has only one root.

(iii) Verify by calculation that this root lies between 2 and 2.5.

(iv) Use an iterative formula based on the equation in part (i) to calculate the value of a correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2007 p3 q6
1893

(i) By sketching a suitable pair of graphs, show that the equation \(2 - x = \ln x\) has only one root.

(ii) Verify by calculation that this root lies between 1.4 and 1.7.

(iii) Show that this root also satisfies the equation \(x = \frac{1}{3}(4 + x - 2 \ln x)\).

(iv) Use the iterative formula \(x_{n+1} = \frac{1}{3}(4 + x_n - 2 \ln x_n)\), with initial value \(x_1 = 1.5\), to determine this root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2006 p3 q6
1894

(i) By sketching a suitable pair of graphs, show that the equation \(2 \cot x = 1 + e^x\), where \(x\) is in radians, has only one root in the interval \(0 < x < \frac{1}{2} \pi\).

(ii) Verify by calculation that this root lies between 0.5 and 1.0.

(iii) Show that this root also satisfies the equation \(x = \arctan\left(\frac{2}{1 + e^x}\right)\).

(iv) Use the iterative formula \(x_{n+1} = \arctan\left(\frac{2}{1 + e^{x_n}}\right)\), with initial value \(x_1 = 0.7\), to determine this root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2005 p3 q7
1895

(i) By sketching a suitable pair of graphs, show that the equation \(\csc x = \frac{1}{2}x + 1\), where \(x\) is in radians, has a root in the interval \(0 < x < \frac{1}{2}\pi\).

(ii) Verify, by calculation, that this root lies between 0.5 and 1.

(iii) Show that this root also satisfies the equation \(x = \sin^{-1} \left( \frac{2}{x+2} \right)\).

(iv) Use the iterative formula \(x_{n+1} = \sin^{-1} \left( \frac{2}{x_n+2} \right)\), with initial value \(x_1 = 0.75\), to determine this root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2004 p3 q5
1896

The diagram shows a sector OAB of a circle with centre O and radius r. The angle AOB is \(\alpha\) radians, where \(0 < \alpha < \frac{1}{2}\pi\). The point N on OA is such that BN is perpendicular to OA. The area of the triangle ONB is half the area of the sector OAB.

  1. Show that \(\alpha\) satisfies the equation \(\sin 2x = x\).
  2. By sketching a suitable pair of graphs, show that this equation has exactly one root in the interval \(0 < x < \frac{1}{2}\pi\).
  3. Use the iterative formula \(x_{n+1} = \sin(2x_n)\), with initial value \(x_1 = 1\), to find \(\alpha\) correct to 2 decimal places, showing the result of each iteration.
problem image 1896
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Nov 2003 p3 q5
1897

(i) By sketching suitable graphs, show that the equation \(\sec x = 3 - x^2\) has exactly one root in the interval \(0 < x < \frac{1}{2}\pi\).

(ii) Show that, if a sequence of values given by the iterative formula \(x_{n+1} = \cos^{-1} \left( \frac{1}{3-x_n^2} \right)\) converges, then it converges to a root of the equation given in part (i).

(iii) Use this iterative formula, with initial value \(x_1 = 1\), to determine the root in the interval \(0 < x < \frac{1}{2}\pi\) correct to 2 decimal places, showing the result of each iteration.

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June 2022 p32 q5
1898

(a) By sketching a suitable pair of graphs, show that the equation \(\ln x = 3x - x^2\) has one real root.

(b) Verify by calculation that the root lies between 2 and 2.8.

(c) Use the iterative formula \(x_{n+1} = \sqrt{3x_n - \ln x_n}\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Mar 2022 p32 q7
1899

(a) By sketching a suitable pair of graphs, show that the equation \(4 - x^2 = \sec \frac{1}{2}x\) has exactly one root in the interval \(0 \leq x < \pi\).

(b) Verify by calculation that this root lies between 1 and 2.

(c) Use the iterative formula \(x_{n+1} = \sqrt{4 - \sec \frac{1}{2}x_n}\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2021 p33 q6
1900

(a) By sketching a suitable pair of graphs, show that the equation \(\cot \frac{1}{2}x = 1 + e^{-x}\) has exactly one root in the interval \(0 < x \leq \pi\).

(b) Verify by calculation that this root lies between 1 and 1.5.

(c) Use the iterative formula \(x_{n+1} = 2 \arctan \left( \frac{1}{1 + e^{-x_n}} \right)\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2020 p31 q5
1901

(a) By sketching a suitable pair of graphs, show that the equation \(\csc x = 1 + e^{-\frac{1}{2}x}\) has exactly two roots in the interval \(0 < x < \pi\).

(b) The sequence of values given by the iterative formula \(x_{n+1} = \pi - \sin^{-1}\left( \frac{1}{e^{-\frac{1}{2}x_n} + 1} \right)\), with initial value \(x_1 = 2\), converges to one of these roots. Use the formula to determine this root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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June 2020 p33 q6
1902

(a) By sketching a suitable pair of graphs, show that the equation \(x^5 = 2 + x\) has exactly one real root.

(b) Show that if a sequence of values given by the iterative formula \(x_{n+1} = \frac{4x_n^5 + 2}{5x_n^4 - 1}\) converges, then it converges to the root of the equation in part (a).

(c) Use the iterative formula with initial value \(x_1 = 1.5\) to calculate the root correct to 3 decimal places. Give the result of each iteration to 5 decimal places.

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Feb/Mar 2020 p32 q3
1903

(a) By sketching a suitable pair of graphs, show that the equation \(\sec x = 2 - \frac{1}{2}x\) has exactly one root in the interval \(0 \leq x < \frac{1}{2}\pi\).

(b) Verify by calculation that this root lies between 0.8 and 1.

(c) Use the iterative formula \(x_{n+1} = \cos^{-1}\left(\frac{2}{4-x_n}\right)\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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Nov 2019 p33 q5
1904

(i) By sketching a suitable pair of graphs, show that the equation \(\ln(x+2) = 4e^{-x}\) has exactly one real root.

(ii) Show by calculation that this root lies between \(x = 1\) and \(x = 1.5\).

(iii) Use the iterative formula \(x_{n+1} = \ln\left( \frac{4}{\ln(x_n + 2)} \right)\) to determine the root correct to 2 decimal places. Give the result of each iteration to 4 decimal places.

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