y=1-cos（2x-π/5）的最大值和最小值以及X的集合

-1<=cos(2x-π/5)<=1
-1<=-cos(2x-π/5)<=1
1-1<=1-cos(2x-π/5)<=1+1
所以最大值=2，最小值=0

y=2,cos(2x-π/5)=-1
2x-π/5=2kπ+π,x=kπ+3π/5
y=0,cos(2x-π/5)=1
2x-π/5=2kπ,x=kπ+π/10

所以
x=kπ+π/10，y最小=0
x=kπ+3π/5，y最大=2

y=1-cos(2x-pi/5)

-1<=cos(2x-pi/5)<=1
-1<=-cos(2x-pi/5)<=1
0<=1-cos(2x-pi/5)<=2
当cos(2x-pi/5)=1,
y有最小值
2x-pi/5=2kpi
x=kpi+pi/10(k是整数)
当cos(2x-pi/5)=-1,
y有最大值
2x-pi/5=pi+2kpi
x=kpi+3pi/5(k是整数)