The distance formula is really just a restatement of the Pythagorean theorem. If we view the change in x and the change in y as the horizontal and vertical legs of a triangle, respectively, then the distance between the two points is the hypotenuse. So,
(change in x)2 + (change in y)2 = (distance)2
Δx2 + Δy2 = D2
From there, if we solve for distance, we find:
D = √(Δx2 + Δy2)
If you have any further questions, please let me know.
