<P> where f (\ displaystyle f) is the distance between the foci, p (\ displaystyle p) and q (\ displaystyle q) are the distances from each focus to any point in the ellipse . </P> <P> The semi-major axis of a hyperbola is, depending on the convention, plus or minus one half of the distance between the two branches; if this is a (\ displaystyle a) in the x-direction the equation is: </P> <Dl> <Dd> (x − h) 2 a 2 − (y − k) 2 b 2 = 1 . (\ displaystyle (\ frac (\ left (x-h \ right) ^ (2)) (a ^ (2))) - (\ frac (\ left (y-k \ right) ^ (2)) (b ^ (2))) = 1 .) </Dd> </Dl> <Dd> (x − h) 2 a 2 − (y − k) 2 b 2 = 1 . (\ displaystyle (\ frac (\ left (x-h \ right) ^ (2)) (a ^ (2))) - (\ frac (\ left (y-k \ right) ^ (2)) (b ^ (2))) = 1 .) </Dd>

How to calculate the semi major axis of a planet