Prove that the square of the orbital period is proportional to the cube of the major axis (kepler's 3rd law) using the following equations (a and b are parameters of elliptical trajectory, T is orbital period, xi is inverse distance from focus to point on elliptical)
έ = C cos (θ - φ) + GMₑ/h²
a = rₚ + rₐ/2
b = √rₚrₐ
T = π/h (rₚ+rₐ) √rₚrₐ
