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Definition df-ur 13154
Description: Define the multiplicative identity, i.e., the monoid identity (df-0g 12713) of the multiplicative monoid (df-mgp 13142) of a ring-like structure. This multiplicative identity is also called "ring unity" or "unity element".

This definition works by transferring the multiplicative operation from the .r slot to the +g slot and then looking at the element which is then the 0g element, that is an identity with respect to the operation which started out in the .r slot.

See also dfur2g 13156, which derives the "traditional" definition as the unique element of a ring which is left- and right-neutral under multiplication. (Contributed by NM, 27-Aug-2011.) (Revised by Mario Carneiro, 27-Dec-2014.)

Assertion
Ref Expression
df-ur 1r = (0g ∘ mulGrp)

Detailed syntax breakdown of Definition df-ur
StepHypRef Expression
1 cur 13153 . 2 class 1r
2 c0g 12711 . . 3 class 0g
3 cmgp 13141 . . 3 class mulGrp
42, 3ccom 4632 . 2 class (0g ∘ mulGrp)
51, 4wceq 1353 1 wff 1r = (0g ∘ mulGrp)
Colors of variables: wff set class
This definition is referenced by:  ringidvalg  13155
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