Question

Simplify (1 − sin x)(1 + sin x).

Answer 1

can you write a simple form of (a+b)(a-b)

use this to write your equation in a way you might recognise...

Answer 2

Is it like square of a sum? (a+b)(a-b)=(a-b)^2

Answer 3

(a-b)(a+b)=a*a-b*b= a^2-b^2

Answer 4

so in your case
a=1
b = sin x

so rewrite the equation a^2-b^2 with those values