Question

Simplifying sec× cos(-×)-sin^2 ×

Answer 1

$\sec x \cos(-x)-\sin^2x = \sec x \cos x - \sin^2x$, since cos is an even function. (This means cos(-x) = cos(x))

$=1-\sin^2x$, since $\sec x \cos x = 1$

$= \cos^2x$, by $\sin^2x+\cos^2x=1$.