Description: Direct proof of pwuninel avoiding functions and thus several ZF axioms. (Contributed by Stefan O'Rear, 22-Feb-2015)
Ref | Expression | ||
---|---|---|---|
Assertion | pwuninel2 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | pwnss | |
|
2 | elssuni | |
|
3 | 1 2 | nsyl | |