The curve C has polar equation r = 2 cos 2θ . Sketch the curve for 0 ≤ θ < 2π .
- The curve C has polar equation r = 2 cos 2θ . Sketch the curve for 0 ≤ θ < 2π .[4]
- Find the exact area of one loop of the curve.[4]
Mark scheme
Marking points from the official mark scheme (May/June 2011). The mark or mark type is shown in brackets.
- [B1B1] Right-hand loop Position and through pole and (2, 0).
- [B1B1] Left-hand loop Position and through pole and (2, π ).
- Deduct 1 mark for extra loops (r < 0).
- [M1] Uses A = 1/2 ∫ r² dθ
- [M1] Uses double angle formula. = ∫ (cos 4θ+1) dθ (LNR)
- [A1] Integrates. = 1/2 [1/4 sin 4θ+θ] (LNR)
- [A1] Inserts any appropriate limits which legitimately give the result. e.g. [1/4 sin 4θ+θ]₀^(π/2) = π/2
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