Need Urgent Trig Help!!

Question

Find the value for sin (θ) if the following conditions hold: cos(2(theta)) = 3/5 and 90(degrees) < (theta) < 180(degrees)

A. (1/25) B. (sqrt5/25) C. (2 sqrt5/5) D. (sqrt5/5)

Answer 1

cos 2θ = 0.6

2cos² θ - 1 = 0.6         double angle formula

2cos² θ = 1.6              add one to both sides

cos² θ = 0.8                divide both sides by 2

cos θ = ±2√5 / 5         root both sides

 

Can you determine the sin θ?