sin2x/(sinx+cosx-1)(sinx-cosx+1)答案确定正确
问题描述：
sin2x/(sinx+cosx-1)(sinx-cosx+1)
答案确定正确
答
(sinx+cosx-1)(sinx-cosx+1)/sin2x =[sinx+(cosx-1)][sinx-(cosx-1)]/sin2x =[(sinx)^2-(cosx-1)^2]/sin2x =[(sinx)^2-(cosx)^2-1+2cosx]/sin2x ={(sinx)^2-(cosx)^2-[(sinx)^2+(cosx)^2]+2cosx}/sin2x =[2cosx-2(co...