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How to prove False from obviously contradictory assumptions

Suppose I want to prove following Theorem:

Theorem succ_neq_zero : forall n m: nat, S n = m -> 0 = m -> False.

This one is trivial since m cannot be both successor and zero, as assumed. However I found it quite tricky to prove it, and I don't know how to make it without an auxiliary lemma:

Lemma succ_neq_zero_lemma : forall n : nat, O = S n -> False.
Proof.
  intros.
  inversion H.
Qed.

Theorem succ_neq_zero : forall n m: nat, S n = m -> 0 = m -> False.
Proof.
  intros.
  symmetry in H.
  apply (succ_neq_zero_lemma n).
  transitivity m.
  assumption.
  assumption.
Qed.

I am pretty sure there is a better way to prove this. What is the best way to do it?

Solution

  • You just need to substitute for m in the first equation:

    Theorem succ_neq_zero : forall n m: nat, S n = m -> 0 = m -> False.
Proof.
intros n m H1 H2; rewrite <- H2 in H1; inversion H1.
Qed.