# 2cosacosb Formula

As we know that there are six trigonometric functions of angles and their names are

1. Sine
2. Cosine
3. Tangent
4. Cotangent
5. Secant
6. Cosecant

These functions are in relation to the right triangle in the following ways:

In a right triangle ABC,

 Sin A = Perpendicular/ Hypotenuse Cos A = Base/ Hypotenuse Tan A = Perpendicular/ Base Sec A = Base/ Perpendicular Cosec A = Hypotenuse/Perpendicular Cot A = Hypotenuse/ Base

## Formula of 2cosacosb

We know that,

cos (A+B) = cos A cos B – sin A sin B ….. (1)

cos (A-B) = cos A cos B + sin A sin B ….. (2)

Adding 1 and 2, we get

cos (A+B) + cos (A-B) = 2 cos A cos B.

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#### Practise This Question

Which of the following laws did Mendel put forth based on his observations in the monohybrid cross?