Theorem baseval

Description: Value of the base set extractor. (Normally it is preferred to work with ( Basendx ) rather than the hard-coded 1 in order to make structure theorems portable. This is an example of how to obtain it when needed.) (New usage is discouraged.) (Contributed by NM, 4-Sep-2011)

	Ref	Expression
Hypothesis	baseval.k	|- K e. _V
Assertion	baseval	|- ( Base ` K ) = ( K ` 1 )

Proof

Step	Hyp	Ref	Expression
1		baseval.k	|- K e. _V
2		df-base	|- Base = Slot 1
3	1 2	strfvn	|- ( Base ` K ) = ( K ` 1 )