# Thread: Finding exact values in quadrants,.

1. ## Finding exact values in quadrants,.

If i have a question saying find the exact value of cos 2 theta given that sin theta = - 3/5 and theta is in quadrant III.
answear is 7/25 but I don't know how to get there explain and I will give you a huge THANKS!

2. $\cos 2\theta =1-2\sin^2\theta$

Then replace $\sin\theta$ with $-\frac{3}{5}$