是2-cos(x/3)?是(2-cosx)/3?还是2-(cosx/3)?呢?分别是:1,x=6k派,k=0,1,2....1/3,x=2k派,k=0,1,2....3/5,x=2k派,k=0,1,2...错了别怪我
最小值是5/3,集合为x=2k派,k=1,2,3......
y的最小值是1,x的取值范围是x=6nπ(n∈整数)
