Skip to main content
Logo image

Section A.4 Trigonometric Identities

Pythagorean Identities.

The following trigonometric identities are useful in solving differential equations:
\(\sin^2(\theta) + \cos^2(\theta) = 1 \)
\(1 + \tan^2(\theta) = \sec^2(\theta) \)
\(1 + \cot^2(\theta) = \csc^2(\theta) \)

Even and Odd Properties.

\(\displaystyle \sin(-\theta) = -\sin(\theta) \)
\(\displaystyle \cos(-\theta) = \cos(\theta) \)
\(\displaystyle \tan(-\theta) = -\tan(\theta) \)
\(\displaystyle \csc(-\theta) = -\csc(\theta) \)
\(\displaystyle \sec(-\theta) = \sec(\theta) \)
\(\displaystyle \cot(-\theta) = -\cot(\theta) \)
You have attempted of activities on this page.