Foci Equation

Finding the foci.

Remember, finding the vertices is quite simple. You simply add and subtract the major value from it's respected coordinate of the center. Horizontal:

and

Vertical:

and

To find the foci it's quite similar. Horizontal:

and

Vertical:

and

The next question you may have is: how do I find c?

, this means, larger square minus the smaller square. As an example, take the ellipse:

. Note that the center is (2,-3) and the vertices are (2,2) and (2,-8). To find the foci, the larger square is 25, and the smaller is 9. so

So the foci are (2,-3

4) which is (2,1) and (2,-7)