Question

find all solutions to the equation
7 sin^2 x - 14 sin x + 2 = -5

Answer 1

call sin x = x. Solve the quadratic equation:
7x^2 - 14x + 7 = 0
x^2 - 2x + 1 = 0
since a + b + c = 0, one real root is 1 and the other is 1/1 = 1.
sin x = 1 = sin Pi/2 --> x = Pi/2