Given that cos theta= -12/13 and theta lies in quad 2

Question

Find the sin2theta

Answer 1

cosθ = -12/13

    

 θ = cos^-1(-12/13)

 θ = 157.38°

 

Since the angle lies in the 2nd quadrant, and cosine is negative in the 2nd quadrant, 

 

θ = 157.38°

 

 

sin2θ = 2sinθcosθ

         = 2sin(157.38)cos(157.38)

         = -0.71