2013 JJC P2 Q1

2013 JJC P2 Q1

7 marks
Prelims

A curve \(C\) has parametric equations

\(x=\left( 1-\sin t \right)\sin t,\quad y=\left( 1-\sin t \right)\cos t,\) for \(-\frac{\pi }{2}\le t\le \frac{\pi }{2}\).

  1. Sketch \(C\), giving the coordinates of any points of intersection with the \(x\)- and \(y\)-axes.[3]
  2. Show that the area of the region enclosed by \(C\) and the \(x\)-axis, \(A\) is \(\displaystyle\displaystyle \displaystyle\int_{\,-\alpha }^{\,\,\beta \,}{\left( \cos t-\sin t\cos t \right)\left( \cos t-2\sin t\cos t \right)\mathrm{d}t}+\displaystyle\displaystyle \displaystyle\int_{\,\,\alpha }^{\,\,\beta }{\left( \sin t-{{\sin }^{2}}t \right)\left( {{\sin }^{2}}t-{{\cos }^{2}}t-\sin t \right)}\ \mathrm{d}t,\) for some \(0\le \alpha ,\ \beta \le \frac{\pi }{2}\). Find the numerical value of \(A\), giving your answer correct to \(3\) decimal places.[4]

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Answer:(i) Sketch with intercepts (−2,0), (0,0), (0,1); (ii) α = π/2, β = 0, A = 2.356 units²

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