If I want determine the specific orbital energy of something orbiting a black hole, will the vis-viva equation still apply? Or will it apply if I replace the euclidean coordinate [itex]r[/itex]with a radial coordinate? None of the above? If the answer to the second question is yes, then what do I make of <math>a</math>, the semi-major axis? Is it converted to a schwarzschild-type coordinate as well?