Q.Find the distance between the points $(-2, -3)$ and $(2, 0)$.

The distance formula, $PQ = \sqrt{(x_2-x_1)^2+(y_2-y_1)^2}$, gives the straight-line distance between two points $P(x_1,y_1)$ and $Q(x_2,y_2)$. It follows from applying the Pythagorean theorem to the right triangle formed by the horizontal and vertical gaps between the two points. Besides computing a plain distance, it is the standard tool for testing whether three given points form an isosceles or a right-angled triangle, or whether the three points are collinear.