Metamath Proof Explorer


Theorem nelaneq

Description: A class is not an element of and equal to a class at the same time. Variant of elneq analogously to elnotel and en2lp . (Proposed by BJ, 18-Jun-2022.) (Contributed by AV, 18-Jun-2022)

Ref Expression
Assertion nelaneq ¬ A B A = B

Proof

Step Hyp Ref Expression
1 elneq A B A B
2 orc ¬ A B ¬ A B ¬ A = B
3 neneq A B ¬ A = B
4 3 olcd A B ¬ A B ¬ A = B
5 2 4 ja A B A B ¬ A B ¬ A = B
6 1 5 ax-mp ¬ A B ¬ A = B
7 ianor ¬ A B A = B ¬ A B ¬ A = B
8 6 7 mpbir ¬ A B A = B