Database
ZF (ZERMELO-FRAENKEL) SET THEORY
ZF Set Theory - add the Axiom of Power Sets
Functions
0nelfun
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funss
Metamath Proof Explorer
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Unicode
Theorem
0nelfun
Description:
A function does not contain the empty set.
(Contributed by
BJ
, 26-Nov-2021)
Ref
Expression
Assertion
0nelfun
⊢
Fun
⁡
R
→
∅
∉
R
Proof
Step
Hyp
Ref
Expression
1
funrel
⊢
Fun
⁡
R
→
Rel
⁡
R
2
0nelrel
⊢
Rel
⁡
R
→
∅
∉
R
3
1
2
syl
⊢
Fun
⁡
R
→
∅
∉
R