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

负3分之2倍根号2.

cos(a+π/6)
=sin[π/2-(a+π/6)]
=sin(π/3-a)
=-sin(a-π/3)
=-1/3