已知sin(a-π/3)=1/3,则cos(a+π/6)等于
问题描述:
已知sin(a-π/3)=1/3,则cos(a+π/6)等于
答
负3分之2倍根号2.
答
cos(a+π/6)
=sin[π/2-(a+π/6)]
=sin(π/3-a)
=-sin(a-π/3)
=-1/3