pub fn reference_triangle_ty() -> Expr
ReferenceTriangle : Type
The reference triangle K̂ = {(ξ,η) ∈ ℝ² : ξ ≥ 0, η ≥ 0, ξ+η ≤ 1}. All physical triangles are images of K̂ under an affine map Fₖ: ξ ↦ Bₖ ξ + bₖ.