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lean4game/server/adam/Adam/Levels/SetTheory/L09_Complement.lean

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import Adam.Metadata
import Mathlib.Data.Set.Basic
Game "Adam"
World "SetTheory"
Level 9
Title "Komplement"
Introduction
"
Das Komplement einer Menge wird als `Aᶜ` (`\\^c`) geschrieben. Wichtige Lemmas
sind `not_mem_compl_iff` und `compl_eq_univ_diff`.
"
open Set
#check not_mem_compl_iff
#check compl_eq_univ_diff
Statement
""
(A : Set ) (h : Aᶜ ⊆ A) : A = univ := by
apply Subset.antisymm
simp only [subset_univ]
intros x hx
by_cases h4 : x ∈ Aᶜ
exact mem_of_subset_of_mem h h4
rw [←not_mem_compl_iff]
exact h4
NewTactic constructor intro rw assumption rcases simp tauto trivial