Metamath Proof Explorer


Theorem issetf

Description: A version of isset that does not require x and A to be distinct. (Contributed by Andrew Salmon, 6-Jun-2011) (Revised by Mario Carneiro, 10-Oct-2016)

Ref Expression
Hypothesis issetf.1 _ x A
Assertion issetf A V x x = A

Proof

Step Hyp Ref Expression
1 issetf.1 _ x A
2 issetft _ x A A V x x = A
3 1 2 ax-mp A V x x = A