dy=2tan(1+X^2)dtan(1+X^2)=2tan(1+X^2)* 1/cos^2(1+X^2)d(1+X^2) =
2tan(1+X^2)* 1/cos^2(1+X^2)*2xdX =4x*sin(1+X^2)/cos^3(1+X^2) *dx