Ever wondered how to find the diagonal of a box, or the space diagonal of a room? Use Pythagoras TWICE! First find the diagonal of the base (2D), then use that as one side of a new right triangle going up (3D). It's the same a² + b² = c² logic, just used in layers.
This introduction covers From Flat to 3D within Pythagoras in 3D for GCSE Mathematics. Revise Pythagoras in 3D in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 2 flashcards. Use this page as part of a wider topic revision path rather than treating it as an isolated fact. It is section 1 of 5 in this topic. Use this introduction to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Pythagoras in 3D
A cuboid has length l, width w, and height h. Which formula gives the length of the space diagonal d?
Describe the two-step method for finding the space diagonal of a cuboid with dimensions l, w, and h.
Quick recall flashcards
3D Pythagoras
d² = x² + y² + z² for space diagonal. Or use 2D Pythagoras twice: first on base, then with height.
3D Pythagoras
Use Pythagoras twice: once for base diagonal, once for 3D diagonal