如题,
问题描述：
如题,
求证:sin2x/ [(sinx+cosx-1)(sinx+1-cosx)] =cot(x/2)
答
sin2x/ [(sinx+cosx-1)(sinx+1-cosx)]=sin2x/ [(sinx-(1-cosx)(sinx+1-cosx)]=sin2x/ [(sin^2x-(1-cosx)^2]=sin2x/ [sin^2x-1-cos^2x+2cosx]=sin2x/ [sin^2x-(sin^2x+cos^2x)-cos^2x+2cosx]=sin2x/ [-2cos^2x+2cosx]...