1) sin (θ-π/2) =-sin (π/2-θ) =-cos θ, cos (θ+π/2) = sin θ, so there is cosθ=2sinθ,

So tanθ= 1/2.

2) The original formula =(sinθ+2cosθ)(sinθ-cosθ)=-5sin? θ =-(sin? θ+4sin？ θ)=-(sin？ θ+cos？ θ)=- 1

2. The question means 0 < θ < 180, 180.

The first two ranges get 90.

So θ = 1 12.5.