Ok, I know the Pythagorean identities but can't seem to solve these two question.

Evaluate. Give exact anwser.

sin² π/6 - tan² π/4 + cos² π/6

so all I can do on this question so far is use the identity sin x + cos x= 1 to get to

1 - tan² π/4

then I am lost.

The next question I have no idea what to do.

Solve the following equation

1 - 2 cos²Θ = -sinΘ, 0<Θ<2π