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Description: Define a structure that puts the multiplication operation of a ring in the addition slot. Note that this will not actually be a group for the average ring, or even for a field, but it will be a monoid, and unitgrp shows that we get a group if we restrict to the elements that have inverses. This allows to formalize such notions as "the multiplication operation of a ring is a monoid" ( ringmgp ) or "the multiplicative identity" in terms of the identity of a monoid ( df-ur ). (Contributed by Mario Carneiro, 21-Dec-2014)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | df-mgp | |- mulGrp = ( w e. _V |-> ( w sSet <. ( +g ` ndx ) , ( .r ` w ) >. ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 0 | cmgp | |- mulGrp |
|
| 1 | vw | |- w |
|
| 2 | cvv | |- _V |
|
| 3 | 1 | cv | |- w |
| 4 | csts | |- sSet |
|
| 5 | cplusg | |- +g |
|
| 6 | cnx | |- ndx |
|
| 7 | 6 5 | cfv | |- ( +g ` ndx ) |
| 8 | cmulr | |- .r |
|
| 9 | 3 8 | cfv | |- ( .r ` w ) |
| 10 | 7 9 | cop | |- <. ( +g ` ndx ) , ( .r ` w ) >. |
| 11 | 3 10 4 | co | |- ( w sSet <. ( +g ` ndx ) , ( .r ` w ) >. ) |
| 12 | 1 2 11 | cmpt | |- ( w e. _V |-> ( w sSet <. ( +g ` ndx ) , ( .r ` w ) >. ) ) |
| 13 | 0 12 | wceq | |- mulGrp = ( w e. _V |-> ( w sSet <. ( +g ` ndx ) , ( .r ` w ) >. ) ) |