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Metamath Proof Explorer

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	⊢ ( Base ‘ ndx ) = 1

Proof

Step	Hyp	Ref	Expression
1		df-base	⊢ Base = Slot 1
2		1nn	⊢ 1 ∈ ℕ
3	1 2	ndxarg	⊢ ( Base ‘ ndx ) = 1