# Difference between revisions of "Trigonometric identities"

Trigonometric identities are used to manipulate trig equations in certain ways. Here is a list of them:

## Pythagorean Identities

• $\displaystyle \sin^2x + \cos^2x = 1$
• $\displaystyle 1 + \cot^2x = \csc^2x$
• $\displaystyle \tan^2x + 1 = \sec^2x$

## Other Identities

• $|1-e^{i\theta}|=2\sin\frac{\theta}{2}$