sin(2π/3+α)=-cosα怎么证明的
问题描述:
sin(2π/3+α)=-cosα怎么证明的
是3π/2 搞错了
答
sin(3π/2+α)
=sin(π+ π/2+α)
= - sin(π/2+α)
= - cosa
或者 套用公式
sin(3π/2+α)=sin(3π/2)cosa+cos(3π/2)sina= -cosa我知道了 把后面的看成整体是吧是的3π/2+α= π+( π/2+α)