Three-Dimensional Pythagorean Theorem

The Pythagorean Theorem works to find the diagonal of a parallopiped. [br][br]Can you see how the theorem extends to work in 3D?
Source: [url=https://www.geogebra.org/alegallardo28]Alejandro Gallardo in Spanish[/url]

Information: Three-Dimensional Pythagorean Theorem