# Cosine Formula

In trigonometry, the law of cosines is also known as the cosine formula or cosine rule, relates the lengths of the sides of a triangle to the cosine of one of its angles.

## Formula for Cosine

The Cosine Formula is,

cos θ=Adjacent/Hypotenuse
• a2 b2 c2 − 2bc.cosA
• ba2 +c− 2ac.cosB
• cab− 2ab.cosC

### Solved Examples

Question 1: Calculate the cosine angle of a right triangle given the adjacent side and hypotenuse are 12 cm and 15 cm respectively ?
Solution:

Given,
Adjacent side = 12 cm
Hypotenuse = 15 cmcoθ = Adjacent/Hypotenuse

coθ = 12 cm/15 cm

coθ = 0.8

#### Practise This Question

The resistivity of all pure metals increase with the rise in temperature.