SOLUTION: Proof: sin ^4x -cos^4x=2sin^2 x-1

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Question 814510: Proof: sin ^4x -cos^4x=2sin^2 x-1
Answer by lwsshak3(11628) About Me  (Show Source):
You can put this solution on YOUR website!
Proof: sin ^4x -cos^4x=2sin^2 x-1
Start with left side:
sin^4x-cos^4x=(sin^2x+cos^2x)(sin^2x-cos^2x)(difference of two squares)
=1*(sin^2x-cos^2x)=sin^2x-(1-sin^2x)=sin^2x-1+sin^2x)
=2sin^x-1
verified: left side=right side