∫1/x(x^2+2)dx=1/2*S1/xdx-1/2*S1/(x^2+2)dx=1/2*ln|x|-1/2根2*S1/（x/根2）^2+1)d(x/根2)=1/2*ln|x|-1/2根2*arctan(2根2)+c
