(1)
f(x)
=cos(-x/2)+sin(π-x/2)
=cos(x/2)+sin(x/2)
=√2[(√2/2)cos(x/2)+(√2/2)sin(x/2)]
=√2[sin(π/4)cos(x/2)+cos(π/4)sin(x/2)]
=√2sin(x+π/4)
则：f(x)的周期
T=2π/1=2π
(2)
设t=x+π/4
则当t属于[2kπ+π/2,2kπ+3π/2]时
f(x)单调递减
即：2kπ+π/2=