Lemma 2.3.2 (Multiplication is commutative). Let \(n\) and \(m\) be natural numbers. Then \(n \times m = m \times n\).
Lemma 2.3.2
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Exercise 2.3.4
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Exercise 2.3.1 (Lemma 2.3.2)
2.3.1. Prove Lemma 2.3.2 (Hint: modify the proofs of Lemmas 2.2.2, 2.2.3 and Proposition 2.2.4)
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Chapter2
Exercise 2.3.1. Prove Lemma 2.3.2