求证sin(3π/2-a)=-cosa
问题描述:
求证sin(3π/2-a)=-cosa
答
sin(3π/2-a)
=sin(3π/2)cosa-cos(3π/2)sina
=-1×cosa-0×sina
=-cosa
答
sin(3π/2-a)=sin(π+π/2-a)=-sin(π/2-a)=-cosa