cosx+1/2≥0
cosx≥-1/2
（2k-1）π+π/3≤x≤（2k+1）π-π/3
tanx-1≥0
tanx≥1
kπ+π/4≤x＜kπ+π/2
所以（2k-1）π+π/3≤x＜（2k-1）π+π/2
或2kπ+π/4≤x＜2kπ+π/2