已知0<x,y<π/2,tanx=3tany.求证x-y≤π/6

问题描述:

已知0<x,y<π/2,tanx=3tany.求证x-y≤π/6

tan(x-y)=(tanx-tany)/(1+tanxtany)=2tany/(1+3tan²y)所以x-y=2ab第二个等号怎么出来的把tanx=3tany代入