(1）当x=π/2+2kπ (k∈z)时有最大值2
当x= -π/2+2kπ (k∈z)时有最小值-2
(2)x=π+2kπ (k∈z)时有最大值7/3
x=2kπ(k∈z)时有最小值5/3