14 lines
439 B
Text
14 lines
439 B
Text
Set: pp::colors
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Set: pp::unicode
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Imported 'macros'
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Using: Nat
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Assumed: Induction
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Proved: Comm1
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Proved: Comm2
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theorem Comm2 : ∀ n m : ℕ, n + m = m + n :=
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λ n : ℕ,
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Induction
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(λ x : ℕ, n + x = x + n)
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(Nat::add_zeror n ⋈ symm (Nat::add_zerol n))
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(λ (m : ℕ) (iH : n + m = m + n),
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Nat::add_succr n m ⋈ subst (refl (n + m + 1)) iH ⋈ symm (Nat::add_succl m n))
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