2x=π/2,y=2
2=a+0+a
所以a=1
f(x)=sin2x+cos2x=√2(√2/2*sin2x+√2/2cos2x)+1
=√2(sin2xcosπ/4+cos2xsinπ/4)+1
=√2sin(2x+π/4)+1
递增是
2kπ-π/2