所求面积=∫(cosx-sinx)dx+∫(sinx-cosx)dx=(sinx+cosx)│+(-cosx-sinx)│=(sin(π/4)+cos(π/4)-sin(0)-cos(0))+(-cos(π/2)-sin(π/2)+cos(π/4)+sin(π/4))=(√2/2+√2/2-0-1)+(-0-1+√2/2+√2/2)=2(√2-1).
