Theorem sylbb2 138

Description: A mixed syllogism inference from two biconditionals. (Contributed by BJ, 21-Apr-2019.)

Hypotheses

Ref	Expression
sylbb2.1	⊢ (𝜑 ↔ 𝜓)
sylbb2.2	⊢ (𝜒 ↔ 𝜓)

Assertion

Ref	Expression
sylbb2	⊢ (𝜑 → 𝜒)

Proof of Theorem sylbb2

Step	Hyp	Ref	Expression
1		sylbb2.1	. 2 ⊢ (𝜑 ↔ 𝜓)
2		sylbb2.2	. . 3 ⊢ (𝜒 ↔ 𝜓)
3	2	biimpri 133	. 2 ⊢ (𝜓 → 𝜒)
4	1, 3	sylbi 121	1 ⊢ (𝜑 → 𝜒)

This proof depends on syntax axioms:   → wi 4   ↔ wb 105

This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108

This proof depends on definitions:  df-bi 117

This theorem is used by:  inffiexmid  7213  ssfirab  7244  ctssexmid  7491  pw1nel3  7591  fsumsplitsnun  12205  wlkm  16751  konigsberglem5  16904  wexmiddiffilem  17214  wexmiddifxylem  17216