The following lesson is written for high school students to develop their understanding of the Pythagorean Theorem (and distance formula) at work in three dimensions. In the IB Mathematics SL curriculum, vectors are to be covered and the magnitude of a vector uses a version of the distance formula but for three dimensions. (The magnitude of a vector is .) The purpose of this Geogebra book is to address the "jump" being made when that formula for magnitude of a vector is introduced. The problem sets are a good way to check for understanding, while the Geogebra demonstrations are a good way to "play" with the math. *You may need to run this Book in Firefox or Safari, rather than Chrome, unless you have enabled WebGL.