Consecutive Turns in a Boundary Cap Are Nonpositive
ProvedProblem97.CGN.CGN4g2_consecutiveTurn_nonpos_of_capBlockconvex-geometryerdos-97-96-countinglean-formalizationordered-capsigned-area
Suppose an ordered cap L is embedded as a boundary block in an enumeration φ, and every increasing triple of indices in φ has strictly negative signed area. Then every three consecutive vertices of L have nonpositive signed area.
Preamble
/- Generated theorem stub from Erdos9796Proof.P97.CGN.CGN4g by Stage 2 proof cut; source SHA-256 c412b95ca627805e0db3a1f0d192f80b93891249e4eb1369844d4f8206dcba79 -/
import Definitions.Def_Erdos9796Counting_Adapter
import Definitions.Def_Erdos9796Counting_CGN_CGN
import Definitions.Def_Erdos9796Counting_CGN_CGN4g
import Definitions.Def_Erdos9796Counting_Foundation
import Mathlib.Data.Finset.Sort
import Mathlib.Logic.Equiv.Fin.Rotate
import Mathlib.Order.Interval.Finset.Fin
open Problem97 Problem97.CGN
/-!
# CGN4g: ordered-cap block packaging
This file adds the closure-plan data carrier for the ordered-cap block cut out
of a global convex-boundary enumeration, together with the theorem wrappers
that are pure packaging.
The geometric producers for the block (`CGN4g1`, `CGN4g3`, `CGN4g4`) remain
separate. The declarations here are the sanctioned interfaces consumed by the
existing CGN6 / CGN7 layers.
-/
open scoped EuclideanGeometry
open scoped InnerProductSpace
variable {A C : Finset ℝ²}Formal statement
theorem Problem97.CGN.CGN4g2_consecutiveTurn_nonpos_of_capBlock
{A C : Finset ℝ²} {n m : ℕ}
{phi : Fin n → ℝ²} {L : OrderedCap m}
(Block : BoundaryCapBlock A C phi L)
(hneg : ∀ {i j k : Fin n}, i < j → j < k →
Problem97.signedArea2 (phi i) (phi j) (phi k) < 0) :
∀ t : ℕ, ∀ ht : t + 2 < m,
Problem97.signedArea2
(L.points ⟨t, by
exact lt_trans
(Nat.lt_add_of_pos_right (by decide : 0 < (2 : ℕ))) ht⟩)
(L.points ⟨t + 1, by
exact lt_trans
(Nat.succ_lt_succ (Nat.lt_add_of_pos_right (by decide : 0 < (1 : ℕ))))
ht⟩)
(L.points ⟨t + 2, by
exact ht⟩) ≤ 0 := by sorrySource