A curve has equation \(y = \frac{4}{3x-4}\) and \(P(2, 2)\) is a point on the curve.
(i) Find the equation of the tangent to the curve at \(P\).
(ii) Find the angle that this tangent makes with the \(x\)-axis.
Solution
(i) To find the equation of the tangent, we first need the derivative \(\frac{dy}{dx}\) of the curve \(y = \frac{4}{3x-4}\).
The derivative is \(\frac{dy}{dx} = -4(3x-4)^{-2} \times 3\).
Substituting \(x = 2\) into the derivative gives the gradient \(m = -3\).
The equation of the tangent at \(P(2, 2)\) is \(y - 2 = -3(x - 2)\).
(ii) The tangent makes an angle \(\theta\) with the \(x\)-axis, where \(\tan \theta = \pm (-3)\).
This gives \(\theta = \pm 108.4^\circ\) (or \(\pm 71.6^\circ\)).
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