Description: Hypothesis builder for elementhood, special case. (Contributed by Mario Carneiro, 10-Oct-2016)
Ref | Expression | ||
---|---|---|---|
Hypothesis | nfeq2.1 | |- F/_ x B |
|
Assertion | nfel2 | |- F/ x A e. B |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nfeq2.1 | |- F/_ x B |
|
2 | nfcv | |- F/_ x A |
|
3 | 2 1 | nfel | |- F/ x A e. B |