| Metamath Proof Explorer |
< Previous
Next >
Related theorems GIF version |
| Description: Extend wff definition to include atomic formulas using the equality predicate. |
| Ref | Expression |
|---|---|
| vx | set x |
| vy | set y |
| Ref | Expression |
|---|---|
| weq | wff x = y |
| Colors of variables: wff set class |