Question

Why is $\cos \left(0\right)=1$?

Answer 1

Finding the value of $\cos \left(0\right)$:

In a right angled triangle, cosine function is the ratio of adjacent side and the hypotaneous.

When one of the angles in a triangle is zero, then the hypotaneous and the adjacent side will coincide with each other.

This results that the ratio of adjacent side and the hypotaneous becomes $1$.

Hence, the value of $\cos \left(0\right)=1$.