∫ln(x+√(1+x^2))dx =xln(x+√(1+x^2) -∫xd(ln(x+√(1+x^2)) =xln(x+√(1+x^2)-∫xdx/√(1+x^2) =xln(x+√(1+x^2)-(1/2)∫d(1+x^2)/√(1+x^2) =xln(x+√(1+x^2)-√(1+x^2)+C
