Question

If cos = 21
29
& sin = 20
29
then find cos2 θ+ sin2 θ

Answer 1

Step-by-step explanation:

Use the identity sin(2θ) = 2sin(θ)cos(θ)

You have sin(θ) = 20/29

Given that θ is acute (meaning it's in the first quadrant), and, the opposite side is 20 and the hypotenuse is 29, you can calculate the adjacent side with the Pythagorean Theorem as 21. That means the cos(θ) = 21/29.

So sin(2θ) = 2(20/29)(21/29) = 840/841