sin(5π-θ)+sin(5π/2-θ)=√7/2
sinθ+cosθ=√7/2,1+sin2θ=7/4,sin2θ=3/4 ,cos2θ=±√7/4
sin(π/2+θ）]^2-[cos(3π/2-θ)]^2=cos^2θ-sin^2θ=cos2θ=±√7/4