Question

This is a trignometry questionhope u will do for me i will mark brainliest..:)​

Answer 1

Step-by-step explanation:

$\cos^{4} x - \sin^{4} x$

$= ( \cos^{2} x + \sin^{2} x)( \cos^{2} x - \sin^{2} x)$

$= (1 - \sin^{2} x + \sin^{2} x)( 1 - \sin^{2} x - \sin^{2} x)$

$= 1 - 2\sin^{2} x$

Note: I replaced all cos^2x terms using the identity

$\cos^{2} x = 1 - \sin^{2} x$