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Angle addition

This original textbook reading covers part of the AP topic. Follow the AP course outline for complete topic instruction and practice.

Angle addition

$\sin (a \pm b) = \sin a \cos b \pm \cos a \sin b$

$\cos (a \pm b) = \cos a \cos b \mp \sin a \sin b$

$\tan (a \pm b) = \frac{\tan a \pm \tan b}{1 \mp \tan a \tan b}$

Related Glossary Terms

Double Angle, Half angle, Trigonometric identities

Index

Chapter 1 - An Overview of Trigonometry

Glossary and deeper reading · 1 refreshers

These editorial refreshers supplement the reading. Definitions and examples are added guidance; original source wording and recorded answers remain in their original context.

Angle addition identity
Angle addition identities express a trigonometric function of a sum using the separate angles. For example, sin(a+b)=sin a cos b+cos a sin b. Using a=π/6 and b=π/3 gives sin(π/2)=1. The addition and subtraction identities also help rewrite expressions for limits, derivatives, and integrals.

Angle addition identity

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