.
So, the major semi-axis length is a = 500/2 = 250 millions kilometers.
The focal distance is 400 millions kilometers; so the linear eccentricity "c" is half of it, i.e. c = 200 millions kilometers.
Then for the minor semi-axis of the ellipse "b" you have
b = = = 150 millions kilometers.
The canonical equation of the ellipse is
+ = 1,
where x a y are coordinates of the orbit in millions of kilometers.
Solved.
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On canonical equation of an ellipse read from the lesson
- Ellipse definition, canonical equation, characteristic points and elements
in this site.