1
y=1/2sin(2x-π/4)
当2x-π/4=2kπ+π/2,
x=kπ+3π/8,k∈Z时,
y取得最大值1/2
当2x-π/4=2kπ-π/2,
x=kπ-π/8,k∈Z时,
y取得最小值-1/2

2
y=sin3x+cos3x
=√2（√2/2sin3x+√2/2cos3x)
=√2sin(3x+π/4)
当3x+π/4=2kπ+π/2,
x=kπ+π/12,k∈Z时,
y取得最大值√2
当3x+π/4=2kπ-π/2,
x=kπ-π/4,k∈Z时,
y取得最小值-√2