Proof of the Pythagorean Theorem in a 3 dimension surface.

Question

Is there any popular, or even not so popular, proof of the Pythagorean Theorem when applied to triangle surfaces in 3 dimensional Euclidean space, that is a triangle in 3d space with vertices at three arbitrary points ($x_1$,$y_1$,$z_1$), ($x_2$,$y_2$,$z_2$), and ($x_3$,$y_3$,$z_3$).

Answer 1

Three distinct points an the Euclidean space always stay on a plane, so, if they forms a rectangular triangle, we can prove the Pythagorean Theorem with one of the usual proofs on the Euclidean plane.