[2kπ+,2kπ+](k∈Z) [2kπ-,2kπ+](k∈Z)
{x|2kπ-≤x≤2kπ+,k∈Z} {x|2kπ+≤x≤2kπ+,k∈Z}
[2kπ+,2k],k∈Z [2kπ﹣,2kπ+],k∈Z
{α|2kπ+<α<2kπ+π,k∈Z}
{α|2kπ+<α<kπ+2π,k∈Z}