SOLUTION: cos(2x) + cos(4x)

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Question 1056970: cos(2x) + cos(4x)
Answer by solve_for_x(190) About Me  (Show Source):
You can put this solution on YOUR website!
The formula to use for this is:

cos%28a%29+%2B+cos%28b%29+=+2cos%28%28a+%2B+b%29%2F2%29cos%28%28a+-+b%29%2F2%29

Applying this to cos(2x) + cos(4x) gives:



Then, since cos(-x) = cos(x), we get:

cos%282x%29+%2B+cos%284x%29+=+2cos%283x%29cos%28x%29+