- #1

flyingpig

- 2,579

- 1

## Homework Statement

An ellipse is a set of all points from two points called a focus (together a foci) has the sum of 2a

|d

_{1}+ d

_{2}| = 2a

A hyperbola is the same except it is difference.

Now my question is, just who came up with these definitions that it must equal to 2a?? Because if I don't remember that it is 2a, then I will never be able to understand the formulas.

## The Attempt at a Solution

attempedt at daydreaming an answer, but failed.