1. 函数y=sinx1−tanxy=\frac{\sin x}{1-\tan x}y=1−tanxsinx的定义域为___{x∣x≠kπ+π2\{x\vert x\ne k\pi +\frac{\pi }{2}{x∣x=kπ+2π[,且]x≠kπ+π4x\ne k\pi +\frac{\pi }{4}x=kπ+4π[,]k∈z}k\in z\}k∈z}___.