Question

3 sin 0 = 3 cos 20
what is the solution set?
​

Answer 1

Explanation:

3 sinθ=3 cos 2θ

sin θ=cos 2θ

sinθ=1-2sin² θ

2sin²θ+sin θ-1=0

2sin²θ+2sinθ-sinθ-1=0

2sin θ(sin θ+1)-1(sin θ+1)=0

(sin θ+1)(2 sin θ-1)=0

sin θ=-1=-sin 90=sin (180+90)

θ=270

or sin θ=1/2=sin 30,sin (180-30)

θ=30,150

solution set is {30,150,270}