Description: Formula-building inference for class substitution. General version of sbcbii . (Contributed by GG, 1-Sep-2025)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | sbceqbii.1 | ⊢ 𝐴 = 𝐵 | |
| sbceqbii.2 | ⊢ ( 𝜑 ↔ 𝜓 ) | ||
| Assertion | sbceqbii | ⊢ ( [ 𝐴 / 𝑥 ] 𝜑 ↔ [ 𝐵 / 𝑥 ] 𝜓 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | sbceqbii.1 | ⊢ 𝐴 = 𝐵 | |
| 2 | sbceqbii.2 | ⊢ ( 𝜑 ↔ 𝜓 ) | |
| 3 | 2 | abbii | ⊢ { 𝑥 ∣ 𝜑 } = { 𝑥 ∣ 𝜓 } |
| 4 | 1 3 | eleq12i | ⊢ ( 𝐴 ∈ { 𝑥 ∣ 𝜑 } ↔ 𝐵 ∈ { 𝑥 ∣ 𝜓 } ) |
| 5 | df-sbc | ⊢ ( [ 𝐴 / 𝑥 ] 𝜑 ↔ 𝐴 ∈ { 𝑥 ∣ 𝜑 } ) | |
| 6 | df-sbc | ⊢ ( [ 𝐵 / 𝑥 ] 𝜓 ↔ 𝐵 ∈ { 𝑥 ∣ 𝜓 } ) | |
| 7 | 4 5 6 | 3bitr4i | ⊢ ( [ 𝐴 / 𝑥 ] 𝜑 ↔ [ 𝐵 / 𝑥 ] 𝜓 ) |