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## Sum and Difference Identities – Formulas and Examples

The sum and difference identities of angles are trigonometric identities used to calculate the values of certain angles. These identities can be used to rewrite the angles as a sum or subtraction of common angles. For example, to calculate the sine or cosine of 15°,...

## Half-angle identities – Formulas, proof and examples

Half-angle identities are trigonometric identities used to simplify trigonometric expressions and calculate the sine, cosine, or tangent of half-angles when we know the values of a given angle. These identities are obtained by using the double angle identities and...

## Double Angle Identities – Formulas, Proof and Examples

Double angle identities are trigonometric identities used to rewrite trigonometric functions, such as sine, cosine, and tangent, that have a double angle, such as 2θ. These identities are derived using the angle sum identities. We have a total of three double angle...

## Fundamental Trigonometric Identities

Trigonometric identities are equations, which are true for any angle used. Trigonometric identities are used to rewrite trigonometric expressions and simplify or solve them. These identities are derived from the fundamental trigonometric functions, sine, cosine, and...

## Formulas for the Trigonometric Identities

Trigonometric identities are useful when we want to rewrite or simplify trigonometric expressions. Trigonometric identities are true for every value that occurs on both sides of an equation. All trigonometric identities are derived from the six fundamental...