2sin²x+sinx-1≥0
(2sinx-1)(sinx+1)≥0
而sinx≥-1,所以sinx+1≥0
所以2sinx-1≥0,即sinx≥1/2
所以2kπ+π/6≤x≤2kπ+5π/6
即定义域为:[2kπ+π/6,2kπ+5π/6] (k∈Z)
2sin²x+sinx-1≥0
(2sinx-1)(sinx+1)≥0
而sinx≥-1,所以sinx+1≥0
所以2sinx-1≥0,即sinx≥1/2
所以2kπ+π/6≤x≤2kπ+5π/6
即定义域为:[2kπ+π/6,2kπ+5π/6] (k∈Z)