Two Complementary-Side Apices Are Impossible
ProvedProblem97.CGN.CGN6e2_not_two_apices_on_complementary_sidecap-witnessconvex-geometrydistance-witnesserdos-97-96-countinglean-formalizationminor-cap
For a convex-independent set containing an ordered cap, two distinct apices equidistant from the cap endpoints cannot both lie strictly on the complementary side of the endpoint chord while avoiding those endpoints.
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_CGN 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.CGN6e2_not_two_apices_on_complementary_side
{m : ℕ} {L : OrderedCap m} {A : Finset ℝ²}
(hconv : ConvexIndep A) (hmem : ∀ t : Fin m, L.points t ∈ A)
{r s : Fin m} (hrs : r < s) {a b : ℝ²}
(haA : a ∈ A) (hbA : b ∈ A)
(hab : a ≠ b)
(har : a ≠ L.points r) (has : a ≠ L.points s)
(hbr : b ≠ L.points r) (hbs : b ≠ L.points s)
(haeq : dist a (L.points r) = dist a (L.points s))
(hbeq : dist b (L.points r) = dist b (L.points s))
(ha_neg : signedArea2 (L.points r) (L.points s) a < 0)
(hb_neg : signedArea2 (L.points r) (L.points s) b < 0) :
False := by sorrySource