### Home > PC3 > Chapter 11 > Lesson 11.2.2 > Problem11-103

11-103.

Rewrite each of the following trigonometric expressions as a single term.

1. $\cos(a)\cos(b) - \sin(a)\sin(b)$

Review the angle sum identity for cosine.

1. $20 \sin(3x)\cos(3x)$

Review the double-angle identity for sine.

1. $\sin(3x)\cos(x) - \cos(3x)\sin(x)$

Review the angle difference identity for sine.

1. $\sin^2(4y) – \cos^2(4y)$

This expression can be rewritten as $−(\cos^2(4y) − \sin^2(4y))$.