Description: If the function's value at an argument is the empty set, then the alternate function value at this argument is the empty set or undefined. (Contributed by AV, 3-Sep-2022)
Ref | Expression | ||
---|---|---|---|
Assertion | afv2fv0 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ioran | |
|
2 | nnel | |
|
3 | afv2rnfveq | |
|
4 | 2 3 | sylbi | |
5 | 4 | eqeq1d | |
6 | 5 | notbid | |
7 | 6 | biimpac | |
8 | 1 7 | sylbi | |
9 | 8 | con4i | |