hi everyone.

I need to consider the following expression:

sin(x)^4 - cos(x)^4 + 2cos(x)^2 = 1

I need to also use following identities to show by hand that this one above is correct: sin^2(x) + cos^2(x) = 1 and a^2 - b^2 = (a - b)(a + b)

Thx for any help.