How do you prove #sin^4x-cos^4x=sin^2x-cos^2x#?

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Nghi N. Share
May 7, 2015

Use the identities:

#a^2 - b^2 = (a - b)(a + b))#
#cos^2 x + sin^2 x = 1#

#sin^4 x - cos^4 x = (sin^2 x - cos^2 x)(sin^2 x + cos^2 x)#
#= sin^2 x - cos ^2 x#

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