The curve C has polar equation r = a(1 + sin θ) for –π < θ < π, where a is a positive constant.
- (i)Sketch C.[2]
- (ii)Find the area of the region enclosed by C.[4]
- (iii)Show that the length of the arc of C from the pole to the point furthest from the pole is given by s = (√2)a ∫ (from -½π to ½π) √(1 + sin θ) dθ.[3]
- (iv)Show that the substitution u = 1 + sin θ reduces this integral for s to (√2)a ∫ (from 0 to 2) 1/√(2-u) du. Hence evaluate s.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- [B1] Sketch of a cardioid
- [B1] Correct orientation and labelled
- [M1]
- [M1]
- [M1A1]
- [M1A1] Uses correct formula for arc length; AG
- [M1]
- [A1] Including limits
- [M1A1]
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