Asked by Rosilyn

Prove that the equation Is an identity.
Sec^4x - Tan^4x = Sec^2x + Tan^2x
Answered by Reiny
LS = (sec^2 x - tan^2x)(sec^2x + tan^2x)
= (1 + tan^2x - tan^2x)(sec^2x + tan^2x)
= 1(sec^2x + tan^2x)
= RS