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[itex] (\frac{dr}{dλ})^2 = E^2 - \frac{L^2}{2r^2} + \frac{GML^2}{r^3} [/itex]

This is an important result for physics, namely it is a radial null geodesic in the Schwarzschild metric. Usually substitutions are made to bring it to a differential equation of dr/d(phi), but I want to know the solution in terms of the affine parameter λ.

I tried separating, solving the radial coordinate and then back-solving for λ, but this was very far from being useful. Mathematica is not much help in solving this ode sadly, but I do recognize that it should have a solution in terms of elliptic functions. I even tried a u=1/r substitution and did not gain any ground that way. Any thoughts or tips on good resources and how difficult this should be to solve are welcomed.