∫ (x / (1+x^2) ) dx 求值,过程非必须,

∫[dx/(e^x(1+e^2x)]dx ∫1+2x/x(1+x)*dx∫1+2x/x(1+x) * dx ∫(x-1)^2dx, ∫x^1/2dx ∫1/x^2+x+1dx ∫1/(x^2+x+1)dx ∫dx/x^2(1-x^2) ∫dx/x^2(1+x^2) ∫X^2/1-x^2 dx. ∫X^2/1-x^2 dx. ∫ (x+arctanx)/(1+x^2) dx ∫（x^2+1/x^4)dx ∫2 -1|x²-x|dx ∫x^2/1+X dx. ∫ xe^x/(1+x)^2 dx ∫dx/[(1-x)x^2] ∫ x/(1+X^2)dx= ∫(2x)/(1+x²)dx