SOLUTION: How to prove that cos3x= 4cos^3x - 3cosx ?

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Question 586529: How to prove that cos3x= 4cos^3x - 3cosx ?
Answer by solver91311(24713) About Me  (Show Source):
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Use the Cosine of the Sum and the Cosine and Sine of Double Angles.







Then



So









Now use the Pythagorean Identity:




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John

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