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Chapter_28
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Imports
Init
Mathlib.Tactic
Imported by
pigeon_hole_principle
Pigeon-hole and double counting
#
TODO
#
statement
Numbers
Claim
Claim
Sequences
Claim
proof
Sums
Claim
Double Counting
Numbers again
Graphs
Theorem
proof
Claim
Sperner's Lemma
proof
Proof of Brouwer's fixed point theorem (for $n = 2$)
source
theorem
pigeon_hole_principle
(n :
ℕ
)
(r :
ℕ
)
(h :
r
<
n
)
(object_to_boxes :
Fin
n
→
Fin
r
)
:
∃ (
box
:
Fin
r
) (
object₁
:
Fin
n
) (
object₂
:
Fin
n
),
object₁
≠
object₂
∧
object_to_boxes
object₁
=
box
∧
object_to_boxes
object₂
=
box