Show that the speed squared written in different standard coordinates systems is:
where:

The algebra for these calculations is a little tedius, but it's good to do them once in your career to convince yourself that these expressions are true!
See: GMM: Curvilinear Coordinates for more discussion of curvilinear coordinates. Note that the labels for the aximuthal and polar coordinates in different for math and physics (\(\phi\) and \(\theta\) are swapped.)