Question

Find the exact value

Given that cos theta = 15/17 with theta quadrant 1 , find sin 2theta and cos 2theta
Plzz help

Answer 1

Since cos theta is 15/17, let a right triangle have a hypotenuse of 17 and a leg of 15. This means that the other is 8.

Sin 2 theta is a double angle identity.

Sin 2 theta = 2 sin theta cos theta = 2(8/17)(15/17) = 240/289

Cos 2theta = cos^2 – sin^2 = (15/17)^2 – (8/17)^2 = 161/289