Table of Contents

## What is the sum and difference identity for tangent?

The sum formula for tangent states that the tangent of the sum of two angles equals the sum of the tangents of the angles divided by 1 minus the product of the tangents of the angles.

## What is the double angle identity for tangent?

tangent double-angle identity can be accomplished by applying the same methods, instead use the sum identity for tangent, first. Therefore, 1+ sin 2x = 1 + sin 2x, is verifiable. The alternative form of double-angle identities are the half-angle identities.

**How many double angle identities are there for tangent?**

They are called this because they involve trigonometric functions of double angles, i.e. sin 2A, cos 2A and tan 2A. and this is our second double angle formula. Similarly tan(A + A) = tan A + tan A 1 − tanA tanA so that tan 2A = 2 tanA 1 − tan2 A These three double angle formulae should be learnt.

**What are the double angle identities?**

The cosine double angle formula tells us that cos(2θ) is always equal to cos²θ-sin²θ. For example, cos(60) is equal to cos²(30)-sin²(30). We can use this identity to rewrite expressions or solve problems.

### What is a sum or difference formula?

The difference formula for cosines states that the cosine of the difference of two angles equals the product of the cosines of the angles plus the product of the sines of the angles. The sum and difference formulas can be used to find the exact values of the sine, cosine, or tangent of an angle.

### What are the sum and difference identities?

Key Equations

Sum Formula for Cosine | cos(α+β)=cosαcosβ−sinαsinβ |
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Sum Formula for Tangent | tan(α+β)=tanα+tanβ1−tanαtanβ |

Difference Formula for Tangent | cos(α−β)=cosαcosβ+sinαsinβ |

Cofunction identities | sinθ=cos(π2−θ) cosθ=sin(π2−θ) tanθ=cot(π2−θ) cotθ=tan(π2−θ) secθ=csc(π2−θ) cscθ=sec(π2−θ) |