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,-34) which is (2,1) and (2,-7)