Question

solve sin^2 x + sin x - 20 = 0

Answer 1

let y=Sinx
y^2+y-20 = 0
can u solve now?

Answer 2

(sin(x) + 5)(sin(x)-4) = 0
=> sin(x) = -5 OR sin(x) = 4
Neither are valid roots for sin function. So, this seems like a bogus problem.