Verify Trigonometric Identity Involving Sine, Cosine, and a Pythagorean Identity

The trigonometric identity to be verified is (1-sin(theta))(1+sin(theta))=cos^2(theta). The LHS is simplified using FOIL to multiply the two binomials containing the sine function. Then the Pythagorean Identity sin^2(x)+cos^2(x) = 1 is used to rewrite the LHS in terms of cos^2(x).

Timestamps
0:00 Introduction. Work on LHS
0:38 Use FOIL
1:56 Use Pythagorean Identity