Description: A class precomposed with its converse includes the identity relation restricted to its range. (Contributed by BJ, 25-Oct-2026)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | idresrnsscocnv2 | |- ( _I |` ran A ) C_ ( A o. `' A ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | idresdmsscocnv1 | |- ( _I |` dom `' A ) C_ ( `' `' A o. `' A ) |
|
| 2 | df-rn | |- ran A = dom `' A |
|
| 3 | 2 | eqcomi | |- dom `' A = ran A |
| 4 | 3 | reseq2i | |- ( _I |` dom `' A ) = ( _I |` ran A ) |
| 5 | cocnvcnv1 | |- ( `' `' A o. `' A ) = ( A o. `' A ) |
|
| 6 | 1 4 5 | 3sstr3i | |- ( _I |` ran A ) C_ ( A o. `' A ) |