Question

Question #4aefe

Answer 1

It comes from the basic algebraic and trigonometric relationships shown below.

Explanation:

`(1-\cos(x))(1+\cos(x))=1-\cos^2(x)` by difference of squares factorization

`=\sin^2(x)` by Pythagorean identity

`=1/\csc^2(x)` by definition of cosecant function as reciprocal of sine