函数有定义则
｛sinx≥0,①
｛cosx-1/2≥0 ②
①==>2kπ≤x≤2kπ+π,k∈Z
②==> cosx≥1/2 ==>2kπ-π/3≤x≤2kπ+π/3,k∈Z
①②取交集：2kπ≤x≤2kπ+π/3,k∈Z
∴定义域是{x|2kπ≤x≤2kπ+π/3,k∈Z}