SOLUTION: how to verify the identity of problem cos^4(x)-sin^4(x)=2cos^2(x)-1

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Question 410613: how to verify the identity of problem
cos^4(x)-sin^4(x)=2cos^2(x)-1
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
cos^4(x)-sin^4(x)=2cos^2(x)-1
..
cos^4-sin^4=2cos^2-1
starting with left-hand side
using difference of squares
(cos^2+sin^2)((cos^2-sin^2)
=(1)(cos^2-sin^2)
=cos^2-(1-cos^2)
=cos^2-1+cos^2
=2cos^2-1
confirmed: Left-hand side=Right-hand side