By definition,  is the orthogonal projection of  onto the -plane, so  is the triangle  with vertices O, B and C, where O is the origin of . Similarly,  and , so the Conant–Beyer theorem says
The orthogonal projection of onto the -plane results in a triangle with vertices O, B and C, where O is the origin of . Similarly,  and , so the Conant–Beyer theorem asserts...