已知sinx=(m-3)/(m+5),cosx=(4-2m)/(m+5)(π/2＜x＜π）,则tanx=
问题描述：
已知sinx=(m-3)/(m+5),cosx=(4-2m)/(m+5)(π/2＜x＜π）,则tanx=
答
tanx
=sinx/cosx
=[(m-3)/(m+5)] / [(4-2m)/(m+5)]
=(m-3)/(4-2m)
=(m-3)/2(2-m)我也是这样，为什么是错的？写 m≠-5 且m≠2