| Exam Board | CAIE |
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| Module | P3 (Pure Mathematics 3) |
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| Year | 2014 |
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| Session | June |
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| Topic | Addition & Double Angle Formulae |
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3 Solve the equation
$$\cos \left( x + 30 ^ { \circ } \right) = 2 \cos x$$
giving all solutions in the interval \(- 180 ^ { \circ } < x < 180 ^ { \circ }\).