English
The altitude foot is the orthogonal projection of a vertex of a simplex onto the opposite face.
Русский
Опорная точка высоты — ортогональная проекция вершины симплекса на противоположную грань.
LaTeX
$$$\text{altitudeFoot}(s,i) = \operatorname{orthogonalProjection}_{\text{faceOpposite}}(s.\text{points}(i))$$$
Lean4
/-- The foot of an altitude is the orthogonal projection of a vertex of a simplex onto the
opposite face. -/
def altitudeFoot {n : ℕ} [NeZero n] (s : Simplex ℝ P n) (i : Fin (n + 1)) : P :=
(s.faceOpposite i).orthogonalProjectionSpan (s.points i)