cos(2x-π/3)=cos(π/3-2x)=sin[π/2-(π/3-2x)]=sin(2x+π/6)

问题描述:

cos(2x-π/3)=cos(π/3-2x)=sin[π/2-(π/3-2x)]=sin(2x+π/6)

由公式cosa=cos(-a)可以得到cos(2x-π/3)=cos(π/3-2x),而由公式cosa=sin(π/2-a)可以得到cos(π/3-2x)=sin[π/2-(π/3-2x)]=sin(2x+π/6)所以cos(2x-π/3)=cos(π/3-2x)=sin[π/2-(π/3-2x)]=sin(2x+π/6)...