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If A + B + C = π, Prove that cos 4A + cos 4B + cos 4C = -1 + 4 cos 2A cos 2B cos 2C. |
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Answer» If A + B + C = π, Prove that cos 4A + cos 4B + cos 4C = -1 + 4 cos 2A cos 2B cos 2C. |
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