已知cosx(π/3+x)=2/3,则sin(x-π/6)=?
问题描述:
已知cosx(π/3+x)=2/3,则sin(x-π/6)=?
答
sin(x-π/6)
=-sin(-x+π/6)
=-cos[π/2-(-x+π/6)]
=-cos(π/3+x)
=-2/3