2sin^2x+cos^2x-sinxcosx
=sin^2x+cos^2x+sin^2x-sinxcosx
=1+sin^2x-sinxcosx
=1+1/2(1-cos2x)-1/2sin2x
=3/2-1/2(sin2x+cos2x)
=3/2-1/2(1-2sin^2x+2cosx-1)
=3/2-1/2(2cos^2x-sin^2x)
=3/2-cos2x
周期是∏;单调增区间：k∏--（k∏+1/2∏）;
单调减区间：（k∏-1/2∏）--k∏;最大值是5/2；
X=k∏+1/2∏时取最大值5/2
还有什么?