Question

Why do we use cosine?

Answer 1

Cosine is the basic trigonometric function.

In a right-angled triangle, cosine is the ratio of the length of the adjacent side to the length of the hypotenuse.

$\cos \theta =\frac{Adjacentside}{Hypotenuse}$

The cosine function is used to find the unknown angle or the unknown length of the sides of a right-angled triangle