Sin2 theta =-1

Answer 1

If you meant
1. sin^2 θ = -1, then there is no solution, (a square of something can't
be negative)
2. sin (2θ) = -1
then 2θ = 3π/2
θ = 3π/4

in general, θ = 3π/4 + kπ , where k is an integer