若tanx=1/2,tan(x-y)==-2/5,则tan(2x-y)
问题描述:
若tanx=1/2,tan(x-y)==-2/5,则tan(2x-y)
答
tan(2x-y)
=[tanx+tan(x-y)]/[1-tanxtan(x-y)]
=(1/10)/(1+1/5)
=1/12