Deduce integral value from area

Questions where you calculate an area using polar coordinates, then use the Cartesian form of the curve to deduce the value of a related Cartesian integral.

3 questions · Challenging +1.8

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CAIE Further Paper 1 2020 June Q5
11 marks Challenging +1.8
5 The curve \(C\) has polar equation \(r = \operatorname { atan } \theta\), where \(a\) is a positive constant and \(0 \leqslant \theta \leqslant \frac { 1 } { 4 } \pi\).
  1. Sketch \(C\) and state the greatest distance of a point on \(C\) from the pole.
  2. Find the exact value of the area of the region bounded by \(C\) and the half-line \(\theta = \frac { 1 } { 4 } \pi\).
  3. Show that \(C\) has Cartesian equation \(\mathrm { y } = \frac { \mathrm { x } ^ { 2 } } { \sqrt { \mathrm { a } ^ { 2 } - \mathrm { x } ^ { 2 } } }\).
  4. Using your answer to part (b), deduce the exact value of \(\int _ { 0 } ^ { \frac { 1 } { 2 } a \sqrt { 2 } } \frac { x ^ { 2 } } { \sqrt { a ^ { 2 } - x ^ { 2 } } } d x\).
OCR FP2 2010 June Q9
13 marks Challenging +1.8
9
\includegraphics[max width=\textwidth, alt={}, center]{074597e7-5bb1-4249-9cfa-784974a6fd2b-4_486_1097_696_523} The diagram shows the curve with equation \(y = \sqrt { 2 x + 1 }\) between the points \(A \left( - \frac { 1 } { 2 } , 0 \right)\) and \(B ( 4,3 )\).
  1. Find the area of the region bounded by the curve, the \(x\)-axis and the line \(x = 4\). Hence find the area of the region bounded by the curve and the lines \(O A\) and \(O B\), where \(O\) is the origin.
  2. Show that the curve between \(B\) and \(A\) can be expressed in polar coordinates as $$r = \frac { 1 } { 1 - \cos \theta } , \quad \text { where } \tan ^ { - 1 } \left( \frac { 3 } { 4 } \right) \leqslant \theta \leqslant \pi$$
  3. Deduce from parts (i) and (ii) that \(\int _ { \tan ^ { - 1 } \left( \frac { 3 } { 4 } \right) } ^ { \pi } \operatorname { cosec } ^ { 4 } \left( \frac { 1 } { 2 } \theta \right) \mathrm { d } \theta = 24\). {www.ocr.org.uk}) after the live examination series.
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OCR Further Pure Core 1 2018 March Q10
14 marks Challenging +1.8
10
  1. (a) A curve has polar equation \(r = 2 - \sec \theta\). Show that the cartesian equation of the curve can be written in the form $$y ^ { 2 } = \left( \frac { 2 x } { x + 1 } \right) ^ { 2 } - x ^ { 2 }$$ The figure shows a sketch of part of the curve with equation \(y ^ { 2 } = \left( \frac { 2 x } { x + 1 } \right) ^ { 2 } - x ^ { 2 }\).
    \includegraphics[max width=\textwidth, alt={}, center]{9d2db858-9c4d-4281-8e8d-9fb5cb11b8ca-4_681_695_667_685}
    (b) Explain why the curve is symmetrical in the \(x\)-axis.
    (c) The line \(x = a\) is an asymptote of the curve. State the value of \(a\).
  2. The enclosed loop shown in the figure is rotated through \(180 ^ { \circ }\) about the \(x\)-axis. Find the exact volume of the solid formed. \section*{END OF QUESTION PAPER}