Description: A syllogism inference from two biconditionals. (Contributed by NM, 12-Mar-1993)
Ref | Expression | ||
---|---|---|---|
Hypotheses | bitr4di.1 | ⊢ ( 𝜑 → ( 𝜓 ↔ 𝜒 ) ) | |
bitr4di.2 | ⊢ ( 𝜃 ↔ 𝜒 ) | ||
Assertion | bitr4di | ⊢ ( 𝜑 → ( 𝜓 ↔ 𝜃 ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | bitr4di.1 | ⊢ ( 𝜑 → ( 𝜓 ↔ 𝜒 ) ) | |
2 | bitr4di.2 | ⊢ ( 𝜃 ↔ 𝜒 ) | |
3 | 2 | bicomi | ⊢ ( 𝜒 ↔ 𝜃 ) |
4 | 1 3 | bitrdi | ⊢ ( 𝜑 → ( 𝜓 ↔ 𝜃 ) ) |