| Exam Board | Edexcel |
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| Module | FP2 (Further Pure Mathematics 2) |
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| Year | 2003 |
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| Session | June |
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| Topic | Complex numbers 2 |
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2. (a) Use de Moivre's theorem to show that
$$\cos 5 \theta = 16 \cos ^ { 5 } \theta - 20 \cos ^ { 3 } \theta + 5 \cos \theta$$
(b) Hence find 3 distinct solutions of the equation \(16 x ^ { 5 } - 20 x ^ { 3 } + 5 x + 1 = 0\), giving your answers to 3 decimal places where appropriate.