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lean4game/server/nng/NNG/Levels/AdvProposition/Level_8.lean

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2 years ago
import NNG.Metadata
import NNG.MyNat.Addition
import Std.Tactic.RCases
import Mathlib.Tactic.LeftRight
Game "NNG"
World "AdvProposition"
Level 8
Title ""
open MyNat
Introduction
"
"
Statement and_or_distrib_left
""
(P Q R : Prop) : P ∧ (Q R) ↔ (P ∧ Q) (P ∧ R) := by
constructor
intro h
rcases h with ⟨hp, hqr⟩
rcases hqr with q | r
left
constructor
assumption
assumption
right
constructor
assumption
assumption
intro h
rcases h with hpq | hpr
rcases hpq with ⟨p, q⟩
constructor
assumption
left
assumption
rcases hpr with ⟨hp, hr⟩
constructor
assumption
right
assumption
Conclusion
"
"