Geometry

# Trigonometric identities

Trigonometric identities (Trig identities) or trigonometric formula describe the relationships between sine, cosine, tangent and cotangent and are used in solving mathematical problems.

The following are double angle formula, values of trigonometric functions, half angle formula, double angle identities, and other formulas. Additionally, the values of trigonometric functions for the most common angles are given.

## Basic trigonometric identities

... preparation ...

## Double angle formula

... preparation ...

## Three angle formula

... preparation ...

## Formula for reducing the degree

... preparation ...

## Formula for reducing the degree

... preparation ...

## Formula for reducing the degree

... preparation ...

## The reduction formula of the degree of the half argument

... preparation ...

... preparation ...

## The subtraction formulas

... preparation ...

## Trigonometric formulas involving Sum to Product Identities

... preparation ...

## Trigonometric formulas involving difference to Product Identities

... preparation ...

## The sum conversion formulas

... preparation ...

## Trigonometry Formulas involving Product identities

... preparation ...

## Formulas for transforming a product of functions to a power

... preparation ...

## Formulas for reducing the degree

... preparation ...

## Universal trigonometric substitution

... preparation ...

## The values of trigonometric functions

 α 0 α° 0° 30° 45° 60° 90° 120° 135° 150° 180° 210° 225° 240° 270° 300° 315° 330° 360° sin α 0 1 0 −1 0 cos α 1 0 −1 0 1 tg α 0 1 − −1 0 1 − −1 0 ctg α − 1 0 −1 − 1 0 −1 −