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Consecutive Minor-Cap Chain Triples Are Nonacute

Proved
Problem97.CGN.CGN6b_nonacute_of_minorCapChainCoords

by mysticflounder · Sep 8, 2026 · Mathlib 0df444a (Lean v4.33.1)

cap-witnessconvex-geometryerdos-97-96-countinglean-formalizationminor-capnonacute-triangle

For a normalized minor-cap chain coordinate model, any three increasing indices form a nonacute angle at the middle point: the inner product of the two vectors from the middle point to the outer points is nonpositive.

Preamble
/- Generated theorem stub from Erdos9796Proof.P97.CGN.CGN6 by Stage 2 proof cut; source SHA-256 87eeea2860c10b6c484c3d7aec9f295605a553c9956e5cc04bbc649402bc9c30 -/
import Definitions.Def_Erdos9796Counting_Adapter
import Definitions.Def_Erdos9796Counting_CGN_CGN6
import Definitions.Def_Erdos9796Counting_Foundation
import Mathlib.Analysis.Convex.Hull
import Mathlib.Analysis.InnerProductSpace.Basic
import Mathlib.Analysis.InnerProductSpace.Orthonormal
import Mathlib.Analysis.InnerProductSpace.TwoDim
import Mathlib.Geometry.Euclidean.PerpBisector
import Mathlib.Order.Interval.Finset.Fin
open Problem97 Problem97.CGN



/-!
# CGN6: normalized minor-cap chain model

This file starts the CGN6 layer named in the updated counterexample-card-ge-nine
prose. It records the normalized minor-cap chain data the prose uses for the
CGN6b slope-product argument: ordered coordinates, endpoint normalization, the
unit-disk bound, and the adjacent-slope bookkeeping.

The actual geometric construction of this model from a concrete MEC cap packet
is still separate. This file only provides the data interface the subsequent
CGN6b / CGN6c proofs will consume.
-/

open scoped EuclideanGeometry
open scoped InnerProductSpace
open scoped BigOperators


























/- ### CGN6norm scaffold

The prose normalization theorem uses an explicit coordinate frame
centered at the chord midpoint and aligned with the chord / inward
normal directions.  The full packet-to-frame bridge is still separate;
this helper records the coordinate map in the exact algebraic form used
by the prose.
-/































-- The normalization proof is large enough to need a higher elaboration budget.
Formal statement
theorem Problem97.CGN.CGN6b_nonacute_of_minorCapChainCoords {m : ℕ} (L : MinorCapChainCoords m) :
    ∀ {i j k : Fin m}, i < j → j < k →
      ⟪point L.X L.Y i - point L.X L.Y j, point L.X L.Y k - point L.X L.Y j⟫_ℝ ≤ 0 := by sorry
Source
https://github.com/mysticflounder/erdos-97-96-formalization/blob/88d43fbd49e26dd52753787835044facf1ed91e5/prove2me/submissions/counting-transfer/platform/Theorems/Thm_Problem97_CGN_CGN6b_nonacute_of_minorCapChainCoords.lean#L1-L141

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