f(x)=2sin²x+2sinxcosx
=1-cos2x+sin2x
=1+√2sin(2x-π/4)
当2x-π/4=π/2,即x=3π/8时,f(x)取最大值1+√2;
当2x-π/4=-π/2,即x=-π/8时,f(x)取最小值1-√2.