# Trigonometric Identities

This is a list of the basic trigonometric identities. You may want to work through a tutorial, with examples and detailed solutions, on Using Trigonometric Identities.

Review

## Pythagoren Identities

1. sin2x + cos2x = 1

2. tan2x + 1 = sec2x

3. 1 + cot2x = csc2x

## Reciprocal Identities

1. csc x = 1 / sin x

2. sec x = 1 / cos x

3. cot x = 1 / tan x

## The Tangent and Cotangent Identities

1. tan x = sin x / cos x

2. cot x = cos x / sin x

## Identities for Negatives

1. sin (-x) = - sin x (the sine function is an odd function)

2. cos (-x) = cos x (the cosine function is an even function)

3. tan (-x) = - tan x (the tangent function is an odd function)

More on
Trigonometric Identities and Their Applications and Trigonometric Formulas and Their Applications