Thread: Finding the coordinates of foci in an ellipse

In the following I determined the value of a to be 6 but I can't find the value of b and therefore cannot find the value of c:

"Find the coordinates of the foci of an ellipse centred at the origin, whose vertices have the coordinates: (8, 0) and (0, -4)."

Any help would be greatly appreciated!
Thanks in advance!

Hello, s3a!

In the following I determined the value of to be 6 . How?
but I can't find the value of . Really?
and therefore cannot find the value of

Find the coordinates of the foci of an ellipse centred at the origin,
whose vertices have the coordinates: (8, 0) and (0, -4).

I don't understand what you were taught . . .


The center is at the origin:
. . So the vertices are at: .

This tell us immediately that: .

And is given by: .