求证:-sinθ=cos(π/2+θ)-sinθ=cos(π/2+θ)

问题描述:

求证:-sinθ=cos(π/2+θ)
-sinθ=cos(π/2+θ)

cos(π/2+θ)=cos(π/2)*cosθ-sin(π/2)*sinθ=-sinθ