既要保证x≠π/2+2kπ,又要分母tanx≠0,所以定义域｛x≠kπ,且x≠π/2+2kπ｝
不懂再问,A.x≠π/2 B。x≠kπ/2 Cx≠kπ D.x≠kπ+π/2B,不好意思忘了和到一块了