f(x)=2(sinx)^2+sinxcosx+(cosx)^2=sinx^2+sinxcosx+1=1/2 (1-cos2x)+1/2sin2x+1=1/2(sin2x-cos2x)+3/2=√2/2(√2/2sin2x-√2/2cos2x)+3/2=√2/2(sin2xcosπ/4-cos2xcosπ/4)+3/2=√2/2sin（2x-π/4）+3/2
