The formula for the distance between two points in the plane extends to points in space, but why?[br]This interactive figure will illustrate why the distance formula is the way it is in space.[br][br]You can drag points A and B. Notice that when you hover over a point, arrows appear showing you how the point will move. Click on the point without dragging to change how the point moves.

[i]Developed for use with Thomas' Calculus, published by Pearson.[/i]