1. The problem statement, all variables and given/known data An ellipse is a set of all points from two points called a focus (together a foci) has the sum of 2a |d1 + d2| = 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. 3. The attempt at a solution attempedt at daydreaming an answer, but failed.