y=1-1/2cos(2x+π/4)取得最大值:
为当cos(2x+π/4)=-1=cos(π+2kπ),y=1-1/2*(-1)=3/2
2x+π/4=π+2kπ 2x=3π/4+2kπ x=3π/8+kπ k∈z
自变量x的集合为﹛x|x=3π/8+kπ,k∈z﹜
y=1-1/2cos(2x+π/4)取得最小值:
为cos(2x+π/4)=1=cos(0+2kπ).y=1-1/2*1=1/2
2x+π/4=2kπ 2x=-π/4+2kπ x=-π/8+kπ k∈z
自变量x的集合为﹛x|x=-π/8+kπ,k∈z﹜