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