SOLUTION: verify of the following is an identyity sin^4x-cos^4x=2sin^2x-1

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Question 400530: verify of the following is an identyity
sin^4x-cos^4x=2sin^2x-1


Answer by Tatiana_Stebko(1539) About Me  (Show Source):
You can put this solution on YOUR website!
%28sinx%29%5E4-%28cosx%29%5E4=2%28sinx%29%5E2-1
Lets work with left side
%28sinx%29%5E4-%28cosx%29%5E4
Use FORMULAa%5E2-b%5E2=%28a-b%29%2A%28a%2Bb%29

Use FORMULAS %28sinx%29%5E2%2B%28cosx%29%5E2=1
_____________%28cosx%29%5E2=1-%28sinx%29%5E2

SO
2%28sinx%29%5E2-1=2%28sinx%29%5E2-1 is an identity