sin(α+3π)+cos(π+α)/sin(－α)-cos(π+α)
=-sin(α)-cos(α) / -sin(α)+cos(α)
= -tan(α)-1 / -tan(α)+1
=(-m-1)/(-m+1)
=(m+1)/(m-1)最后这个不能约分么(m+1)/(m-1) ？不能啊