sin(π/4-x)为什么等于cos(x+π/4)
问题描述:
sin(π/4-x)为什么等于cos(x+π/4)
答
sin(π/4-x)=sin(π/4)cosx-cos(π/4)sinx=(√2/2)cosx-(√2/2)sinx;
cos(x+π/4)=cosxcos(π/4)-sinxsin(π/4)=(√2/2)cosx-(√2/2)sinx;