So I have this math problem: Using the ellipse x^2/a^2 + y^2/b^2 = 1 and assuming that a>b, determine two formulae that calculate the distance from a point on the ellipse to each of the foci. Use the formulae to show that the sum of the distances is 2a. I know that the foci are at (sqrt(a^2-b^2), 0) and (-sqrt(a^2-b^2), 0), but I can't get a formula for the distance of a point to them. I was able to get this extremely long and ugly value, but I'm unable to simplify it and show that it will add to 2a. Any suggestions? Thanks in advance.