Theorem tsetndx

Description: Index value of the df-tset slot. (Contributed by Mario Carneiro, 14-Aug-2015) (New usage is discouraged.)

	Ref	Expression
Assertion	tsetndx	⊢ ( TopSet ‘ ndx ) = 9

Proof

Step	Hyp	Ref	Expression
1		df-tset	⊢ TopSet = Slot 9
2		9nn	⊢ 9 ∈ ℕ
3	1 2	ndxarg	⊢ ( TopSet ‘ ndx ) = 9