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Problem 528
528
(i) Sketch the graph of the curve \(y = 3 \sin x\), for \(-\pi \leq x \leq \pi\).
The straight line \(y = kx\), where \(k\) is a constant, passes through the maximum point of this curve for \(-\pi \leq x \leq \pi\).
(ii) Find the value of \(k\) in terms of \(\pi\).
(iii) State the coordinates of the other point, apart from the origin, where the line and the curve intersect.
Solution
(i) The graph of \(y = 3 \sin x\) is a sine wave with amplitude 3, oscillating between -3 and 3, over the interval \(-\pi \leq x \leq \pi\). The maximum point is at \(x = \frac{\pi}{2}\), where \(y = 3\).
(ii) The line \(y = kx\) passes through the maximum point \(\left( \frac{\pi}{2}, 3 \right)\). Substituting into the line equation gives:
\(3 = k \left( \frac{\pi}{2} \right)\)
Solving for \(k\):
\(k = \frac{6}{\pi}\)
(iii) To find the other intersection point, set \(y = 3 \sin x = kx\) and solve for \(x\):