What values of theta between 0 and 2pi solve the following equation?

Question

sin squared (2theta)-sin(2theta)-2=0

NOTE: if you choose to plot this, a good WINDOW is (0,2pi) x (-3,3).

Answer 1

if you let x=sin(2θ) you have

x^2-x-2=0
(x-2)(x+1) = 0
so,
sin(2θ) = -1
2θ = 3π/2,7π/2
θ = 3π/4,7π/4