How to solve for a different variable

I am trying to solve for a and e in terms of rpark, but MATLAB is giving me an answer for rpark and e in terms of a.

rpark = 1750.5:.01:10000;
syms a e rpark
S = solve(a == (rmoon*(1+e*cos(-20)))/(1-e^2), a == (rpark*(1-e))/(1-e^2));
S.a
S.e

If anyone knows how to correct this it would be greatly appreciated.

Answer 1

[Star Strider]

Try this:

syms a e rpark rmoon 
[Sa,Se] = solve(a == (rmoon*(1+e*cos(-20)))/(1-e^2), a == (rpark*(1-e))/(1-e^2), [a,e])

returning:

Sa =
-(rpark*(7351352886077503*rmoon + 18014398509481984*rpark))/(10663045623404481*rmoon - 36028797018963968*rpark)

Se =
-(18014398509481984*(rmoon - rpark))/(7351352886077503*rmoon + 18014398509481984*rpark)