Question

The Pythagorean Identity states that:

(sin x)2 + (cos x)2 = 1
Given sin 0 = 2/5 find cos 0

Answer 1

cos (theta) = √21/5

Explanation:

sin (theta) = 2/5

(sin (theta))^2 = 4/25

4/25 + (cos (theta))^2 = 1

(cos (theta))^2 = 1 - 4/25 = 21/25

cos (theta) = √21/5