Theorem mtbii 664

Description: An inference from a biconditional, similar to modus tollens. (Contributed by NM, 27-Nov-1995.)

Hypotheses

Ref	Expression
mtbii.min	⊢ ¬ 𝜓
mtbii.maj	⊢ (𝜑 → (𝜓 ↔ 𝜒))

Assertion

Ref	Expression
mtbii	⊢ (𝜑 → ¬ 𝜒)

Proof of Theorem mtbii

Step	Hyp	Ref	Expression
1		mtbii.min	. 2 ⊢ ¬ 𝜓
2		mtbii.maj	. . 3 ⊢ (𝜑 → (𝜓 ↔ 𝜒))
3	2	biimprd 157	. 2 ⊢ (𝜑 → (𝜒 → 𝜓))
4	1, 3	mtoi 654	1 ⊢ (𝜑 → ¬ 𝜒)

Syntax hints:  ¬ wn 3   → wi 4   ↔ wb 104

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 105  ax-ia2 106  ax-ia3 107  ax-in1 604  ax-in2 605

This theorem depends on definitions:  df-bi 116

This theorem is referenced by:  onsucelsucexmid  4453  nntri2  6398  nntri3  6401  nndceq  6403  inffiexmid  6808  genpdisj  7355  ltposr  7595  hashennn  10558  fsumsplit  11208  sumsplitdc  11233