原式=(1/2)*∫arctan^xd(x^)=(1/2)*arctan^x*x^-(1/2)*∫x^d(arctan^x)=x^*arctan^x/2 -(1/2)*∫x^*[2*arctanx/(1+x^)]dx=x^*arctan^x/2-∫[x^/(1+x^)]*arctanx*dx=x^*arctan^x/2-∫arctanxdx+∫arctanxdx/(1+x^)=x^...