Does this identity exist? If so, what is it equivalent to? -sin^(2)x+cos^(2)x = ?

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Answer 1 · 2018-03-18T22:46:26

#cos(2x)#

Yes this is an identity:

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

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

#cosxcosx-sinxsinx=#

Look familiar yet?

#cosxcosx-sinxsinx= cos(2x)#

Answer 2 · 2018-03-18T22:48:06

#-sin^2x+cos^2x#

#=cos^2x-sin^2x#

#=cos^2x-(1-cos^2x)#

#=2cos^2x-1#

#=cos(2x)#