SOLUTION: (sinx+cosx)²=3/4.Find cos²2x.

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Question 1104682: (sinx+cosx)²=3/4.Find cos²2x.
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


(1) Expand the expression on the left in the given equation.

%28sinx%2Bcosx%29%5E2+=+sinx%5E2%2B2sinx%2Acosx%2Bcosx%5E2+=+1%2B2sinx%2Acosx+=+1%2Bsin2x

Then
1%2Bsin2x+=+3%2F4
sin2x+=+-1%2F4

Then find (cos(2x))^2 using %28sin%282x%29%29%5E2%2Bcos%282x%29%5E2+=+1