若cos2X+(i+tanX)i是纯虚数,则X的取值是?
问题描述:
若cos2X+(i+tanX)i是纯虚数,则X的取值是?
我求得X=π/4+kπ且X不等于π/4+2kπ,不知如何取值!
答
cos2X=0且tanX≠-1
2x=kπ+π/2且x≠kπ-π/4
得X=π/4+kπ/2且X≠kπ-π/4