sinx+cosx+1=√2sin(x+π/4)+1≠0
则 sin(x+π/4)≠-√2/2
所以 x+π/4≠-3π/4+2kπ和x+π/4≠-/π4+2kπ
x≠2kπ-π与x≠2kπ-/π2