dT:=x/(z*sqrt(x^2+y^2)*(1+(x^2+y^2)/z^2));

NiM+SSNkVEc2IioqSSJ4R0YlIiIiSSJ6R0YlISIiLCYqJEYnIiIjRigqJEkieUdGJUYtRigjRipGLSwmRihGKComRitGKEYpISIjRihGKg==

diff(dT,x);

NiMsKCooSSJ6RzYiISIiLCYqJEkieEdGJiIiIyIiIiokSSJ5R0YmRitGLCNGJ0YrLCZGLEYsKiZGKEYsRiUhIiNGLEYnRiwqKkYqRitGJUYnRigjISIkRitGMEYnRicqKkYqRitGJUY1RihGL0YwRjJGMg==