Question

How do you simplify `( 1 - cosx) ( 1 + cosx)`?

Answer 1

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

Explanation:

From Pythagoras theorem we get:

`sin^2 x + cos^2 x = 1`

So:

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