f(x)=sinx+cosx=√2（√2/2sinx+√2/2cosx)=√2(sinxcosπ/4+cosxsinπ/4)=√2sin(x+π/4)∴当x+π/4=2kπ-π/2,k∈Zx=2kπ-3π/4,k∈Z时,f(x)取得最小值-√2此时X的集合为{ x|x=2kπ-3π/4,k∈Z}【夕阳无限好】团队...���ʣ�Kȡʲôֵk∈Z,Z是整数集k是整数