Theorem basendx

Description: Index value of the base set extractor. (Contributed by Mario Carneiro, 2-Aug-2013) Use of this theorem is discouraged since the particular value 1 for the index is an implementation detail, see section header comment mmtheorems.html#cnx for more information. (New usage is discouraged.)

	Ref	Expression
Assertion	basendx	$$⊢{\mathrm{Base}}_{\mathrm{ndx}}=1$$

Proof

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