SOLUTION: Find cos&#952; if sin&#952; = 3/5 and 90° < &#952; <180°. Thank You

Algebra ->  Trigonometry-basics -> SOLUTION: Find cos&#952; if sin&#952; = 3/5 and 90° < &#952; <180°. Thank You       Log On


   

Question 42648: Find cosθ if sinθ = 3/5 and 90° < θ <180°.
Thank You
Answer by fractalier(6550) About Me  (Show Source):
You can put this solution on YOUR website!
Let q be theta...
Since sin^2 q + cos^2 q = 1, we know that
cos^2 q = 1 - sin^2 q
cos^2 q = 1 - (3/5)^2
cos^2 q = 1 - 9/25 = 16/25 and then
cos q = 4/5
But in the 2nd quadrant, cos q is negative so the answer is
-4/5