Solve y′=1/(1+x2)y' = 1/(1+x^2)y′=1/(1+x2).
y=tan(x)+Cy = \tan(x) + Cy=tan(x)+C
y=ln(1+x2)+Cy = \ln(1+x^2) + Cy=ln(1+x2)+C
y=arctan(x)+Cy = \arctan(x) + Cy=arctan(x)+C
y=1/xy = 1/xy=1/x