Metamath Proof Explorer


Theorem f10

Description: The empty set maps one-to-one into any class. (Contributed by NM, 7-Apr-1998)

Ref Expression
Assertion f10 :1-1A

Proof

Step Hyp Ref Expression
1 f0 :A
2 funcnv0 Fun-1
3 df-f1 :1-1A:AFun-1
4 1 2 3 mpbir2an :1-1A