SOLUTION: Verify the identity. Please help cos 4u = cos^2 2u - sin^2 2u

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Question 1106830: Verify the identity. Please help
cos 4u = cos^2 2u - sin^2 2u
Answer by greenestamps(13203) About Me  (Show Source):
You can put this solution on YOUR website!


This one doesn't involve any manipulation of the expressions -- just a change in variable.

cos(2x) = (cos(x))^2 - (sin(x))^2

so

cos(4u) = (cos(2u))^2-sin(2u))^2.