Definition df-ur 19252

Description: Define the multiplicative neutral element of a ring. This definition works by extracting the 0_g element, i.e. the neutral element in a group or monoid, and transferring it to the multiplicative monoid via the mulGrp function (df-mgp 19240). See also dfur2 19254, 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

Step	Hyp	Ref	Expression
1		cur 19251	. 2 class 1r
2		c0g 16713	. . 3 class 0g
3		cmgp 19239	. . 3 class mulGrp
4	2, 3	ccom 5559	. 2 class (0g ∘ mulGrp)
5	1, 4	wceq 1537	1 wff 1r = (0g ∘ mulGrp)

This definition is referenced by:  ringidval  19253  prds1  19364  pws1  19366