Description: Define the Godel-set of equivalence. Here the arguments U and V are also Godel-sets corresponding to smaller formulas. Note that this is aclass expression, not a wff. (Contributed by Mario Carneiro, 14-Jul-2013)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | df-gobi | |- <->g = ( u e. _V , v e. _V |-> ( ( u ->g v ) /\g ( v ->g u ) ) ) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 0 | cgob | |- <->g | |
| 1 | vu | |- u | |
| 2 | cvv | |- _V | |
| 3 | vv | |- v | |
| 4 | 1 | cv | |- u | 
| 5 | cgoi | |- ->g | |
| 6 | 3 | cv | |- v | 
| 7 | 4 6 5 | co | |- ( u ->g v ) | 
| 8 | cgoa | |- /\g | |
| 9 | 6 4 5 | co | |- ( v ->g u ) | 
| 10 | 7 9 8 | co | |- ( ( u ->g v ) /\g ( v ->g u ) ) | 
| 11 | 1 3 2 2 10 | cmpo | |- ( u e. _V , v e. _V |-> ( ( u ->g v ) /\g ( v ->g u ) ) ) | 
| 12 | 0 11 | wceq | |- <->g = ( u e. _V , v e. _V |-> ( ( u ->g v ) /\g ( v ->g u ) ) ) |