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