### Distance formula: $d = \sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$

In this lesson, we will learn how to use the distance formula to calculate the distance between two points on a graph when you know the coordinates of both points. Distance formula is actually derived from a very basic concept that we learned in geometry: Pythagorean Theorem, ${a^2} + {b^2} = {c^2}$.