y=√tanx
x≠kπ+π/2(k∈Z)
tanx≥0
kπ≤x＜kπ+π/2(k∈Z)
所以定义域是{x|kπ≤x＜kπ+π/2(k∈Z)}
求定义域关键是找出使函数没有意义的点.定义域后面为什么X＜Kπ+π/2而不是X≠kπ+π/2因为根号内的要大于0，所以它不单单≠kπ+π/2，还要满足kπ≤x＜kπ+π/2，写在一起就是kπ≤x＜kπ+π/2咯