{sec^2(x/y)}/{tan(x/y)}=?
问题描述：
{sec^2(x/y)}/{tan(x/y)}=?
答
tan^2(A)+1=sec^2(A) 原式=[tan^2(x/y)-1]/tan(x/y) =tan(x/y)-1/tan(x/y) =1/[sin(x/y)cos(x/y)] 2sinAcosA=sin(2A) =2/sin(2x/y) =2csc(2x/y)