Confused as why these two formulas do not match up. Or do they???(adsbygoogle = window.adsbygoogle || []).push({});

http://www.geocities.com/thesciencefiles/ellipse/facts.html

c^2=a^2-b^2

This does not seem to match up with the fact that the focal point should be 1/2 the distance of the radius of curvature.

If you make a = b in the elliptical formula, you will essentially be making a circle, and in that case the focal point would be zero or at the center according to the formula.

But this is not true, the focal point should be 1/2 the radius.

Thanks

Nautica

**Physics Forums | Science Articles, Homework Help, Discussion**

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Focal Points

**Physics Forums | Science Articles, Homework Help, Discussion**