
$$
    {{x^2}\over{a^2}} + {{y^2}\over{b^2}} = 1
$$

$$
    r  =  {{ a (1 - e^2) } \over { 1 + e \cos\theta }}
$$

$$
    b^2 = a^2(1 - e^2)
$$

   
$$
    r = a ( 1 - e \cos E ) 
$$

$$ 
    \tan({{v}\over{2}}) = { \sqrt{{1 + e}\over{1 - e}} \tan({{E}\over{2}}) }
$$

$$
    n = {{2 \pi } \over {P} }
$$

$$
    E - e \sin(E) = (t - T) n
$$

$$
    E  =  M + \sum_{k = 1}^{\infty} {{2}\over{k}} J_k (ke) \sin(kM) 
$$




\bye
