CAIE FP1 2008 November — Question 3 6 marks

Exam BoardCAIE
ModuleFP1 (Further Pure Mathematics 1)
Year2008
SessionNovember
Marks6
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicPolar coordinates
TypeArea of region with line boundary
DifficultyStandard +0.8 This is a Further Maths polar coordinates question requiring sketching and area calculation. While the integral setup is standard (½∫r²dθ), students must correctly handle the algebraic form r=(π/2-θ)², expand it carefully, and integrate a polynomial in θ. The algebra is moderately involved and errors are easy to make, placing this above average difficulty but not exceptionally hard for FM students.
Spec4.09a Polar coordinates: convert to/from cartesian4.09b Sketch polar curves: r = f(theta)4.09c Area enclosed: by polar curve

3 The curve \(C\) has polar equation $$r = \left( \frac { 1 } { 2 } \pi - \theta \right) ^ { 2 } ,$$ where \(0 \leqslant \theta \leqslant \frac { 1 } { 2 } \pi\). Draw a sketch of \(C\). Find the area of the region bounded by \(C\) and the initial line, leaving your answer in terms of \(\pi\).

AnswerMarks
Approximately correct curve passing through the pole, \(O\), and the point \(A(\pi^2/4, 0)\)B1
Negative gradient at \(A\)B1
Correct form at \(O\)B1
Area \(= (1/2)\int_0^{\pi/2} (\pi/2 - \theta)^4 d\theta\)M1
\(= -(1/10)\left[\pi/2 - \theta\right]_0^{\pi/2}\)A1
\(= \pi^5/320\)A1
Approximately correct curve passing through the pole, $O$, and the point $A(\pi^2/4, 0)$ | B1 |

Negative gradient at $A$ | B1 |

Correct form at $O$ | B1 |

Area $= (1/2)\int_0^{\pi/2} (\pi/2 - \theta)^4 d\theta$ | M1 |

$= -(1/10)\left[\pi/2 - \theta\right]_0^{\pi/2}$ | A1 |

$= \pi^5/320$ | A1 |
3 The curve $C$ has polar equation

$$r = \left( \frac { 1 } { 2 } \pi - \theta \right) ^ { 2 } ,$$

where $0 \leqslant \theta \leqslant \frac { 1 } { 2 } \pi$. Draw a sketch of $C$.

Find the area of the region bounded by $C$ and the initial line, leaving your answer in terms of $\pi$.

\hfill \mbox{\textit{CAIE FP1 2008 Q3 [6]}}