In this video, we derive distance formulae for 2D and 3D using Pythagoras theorem. We have one right triangle in 2D and 2 right triangles in 3D. We then practice finding distance between two points using visualisation and also using the formula. We consider one application of distane formula - proving collinearity of three points. Desmos link for the animations used in the video: Courses on Khan Academy are always 100% free. Start practicing—and saving your progress—now! ( :introduction-to-three-dimensional-geometry-ncert-new/xea4762213f311c5e:untitled-1055/e/distance-between-two-points) Timestamps: 00:00 Formulae for distances in 2D and 3D 00:58 Deriving distance formula for 2D 02:32 Deriving distance formula for 3D 05:31 Practice problem - distance between two points 08:50 Proving collinearity using distance formula Khan Academy India is a nonprofit organization with the mission of providing a free, world-class education for anyone, anywhere. We have videos and exercises that have been translated into multiple Indian languages, and 15 million people around the globe learn on Khan Academy every month. Support Us: Created by Ashish Gupta