# Foci Calculator

The foci calculator helps determine the foci of an ellipse based on its center and semi-major and semi-minor axes.

Enter the x coordinates, y coordinates, the value of a, and the value of b, to find the first focus F1 and the second focus F2.

In case you’re unaware, the foci of an ellipse are the reference points that define the shape. They can be found along the major axis, which cuts through its longer dimension.

- c = ā(a2 ā b2).
- The standard equation of the ellipse is (x2/a2) + (y2/b2) = 1.

You might want to determine the half-angle or octagon side values.

**References**

- 8.1 – Conics. (n.d.). 8.1 – Conics. https://people.richland.edu/james/lecture/m116/conics/conics.html
- Ellipse foci review (article) | Khan Academy. (n.d.). Khan Academy. https://www.khanacademy.org/math/precalculus/x9e81a4f98389efdf:conics/x9e81a4f98389efdf:ellipse-foci/a/ellipse-foci-review