Theorem plusgndx

Description: Index value of the df-plusg slot. (Contributed by Mario Carneiro, 14-Aug-2015)

	Ref	Expression
Assertion	plusgndx	$$⊢{+}_{\mathrm{ndx}}=2$$

Proof

Step	Hyp	Ref	Expression
1		df-plusg	$$⊢{+}_{𝑔}=\mathrm{Slot}2$$
2		2nn	$$⊢2\in \mathbb{N}$$
3	1 2	ndxarg	$$⊢{+}_{\mathrm{ndx}}=2$$