TES sorry again for bother you, one final question

You said that I should parametrize the cone as x=ucosv, y=usinv and z=z to find the Jacobian. Firstly, the equation of a cone is x^2+y^2 = z^2, but if I take x^2 + y^2 with the above parametrization I get u^2, and z=z not u.

Secondly, I found a different matrix for the Jacobian than you, namely [cosv, -usinv, 0 ; sinv, ucosv, 0; 0 0 1] where the ; is between each row (not column) of my matrix. In the matrix above you wrote my rows as your columns.

Thanks again!