Lesson 4

Add the following terms to your copy of Glossary Terms:

• sum identity
• difference identity
• double-angle identity

Add the following identities to your copy of Formula Sheet:

• sin (A + B) = sin A cos B + cos A sin B
• cos (A + B) = cos A cos B − sin A sin B
• 
• sin (A − B) = sin A cos B − cos A sin B
• cos (A − B) = cos A cos B + sin A sin B
• 
• sin 2A = 2 sin A cos A
• cos 2A = cos2 A − sin2 A
• cos 2A = 2 cos2 A − 1
• cos 2A = 1 − 2 sin2 A
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