Hello, gumby456m!
Verify: .
Verify by transforming one side into the other:
cos^4 x- sin^4 x =cos^2 x-sin^2 x
ive tried transforming the left side to the right side
(cos^2 x)(cos^2 x)-(sin^2 x)(sin^2 x)
but can't figure out how to proceed
thanks for any help