∫arctan(x+1)dx=xarctan(x+1)-∫xdarctan(x+1)=xarctan(x+1)-∫x*1/[1+(x+1)^2]dx=xarctan(x+1)-∫x/(x^2+2x+2)dx=xarctan(x+1)-1/2∫(2x+2)/(x^2+2x+2)dx+∫1/(x^2+2x+2)dx=xarctan(x+1)-1/2∫(2x+2)/(x^2+2x+2)dx...