| Mathbox for Alexander van der Vekens |
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| Mirrors > Home > MPE Home > Th. List > Mathboxes > wich | Structured version Visualization version GIF version | ||
| Description: Extend wff notation to include the property of a wff 𝜑 that the setvar variables 𝑥 and 𝑦 are interchangeable. Read this notation as "𝑥 and 𝑦 are interchangeable in wff 𝜑". |
| Ref | Expression |
|---|---|
| wph | wff 𝜑 |
| vx | setvar 𝑥 |
| vy | setvar 𝑦 |
| Ref | Expression |
|---|---|
| wich | wff [𝑥⇄𝑦]𝜑 |
| Colors of variables: wff setvar class |
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