A problem on my homework: We learn early on that "the shortest distance between two points is a straight line." Let's prove it...Using the Euler equation, compute the extrema of ∫sqrt(1 + (dy/dx)2)dx from x1 to x2 ...show that this corresponds to lines "y = mx +b". Euler had a lot of different equations. I recognize this as the formula for calculating the length of a graph but that's not what I'm being asked to do. Does anyone what formula this is referring to? Thanks!