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Mirrors > Home > MPE Home > Th. List > sbcovOLD | Structured version Visualization version GIF version |
Description: Obsolete version of sbcov 2253 as of 26-Aug-2025. (Contributed by NM, 14-May-1993.) (Revised by GG, 7-Aug-2023.) (Proof modification is discouraged.) (New usage is discouraged.) |
Ref | Expression |
---|---|
sbcovOLD | ⊢ ([𝑦 / 𝑥][𝑥 / 𝑦]𝜑 ↔ [𝑦 / 𝑥]𝜑) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | sbcom3vv 2094 | . 2 ⊢ ([𝑦 / 𝑥][𝑥 / 𝑦]𝜑 ↔ [𝑦 / 𝑥][𝑦 / 𝑦]𝜑) | |
2 | sbid 2252 | . . 3 ⊢ ([𝑦 / 𝑦]𝜑 ↔ 𝜑) | |
3 | 2 | sbbii 2073 | . 2 ⊢ ([𝑦 / 𝑥][𝑦 / 𝑦]𝜑 ↔ [𝑦 / 𝑥]𝜑) |
4 | 1, 3 | bitri 275 | 1 ⊢ ([𝑦 / 𝑥][𝑥 / 𝑦]𝜑 ↔ [𝑦 / 𝑥]𝜑) |
Colors of variables: wff setvar class |
Syntax hints: ↔ wb 206 [wsb 2061 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1791 ax-4 1805 ax-5 1907 ax-6 1964 ax-7 2004 ax-12 2174 |
This theorem depends on definitions: df-bi 207 df-an 396 df-ex 1776 df-sb 2062 |
This theorem is referenced by: (None) |
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