Metamath Proof Explorer

Theorem 1no

Description: Ordinal one maps to a surreal number. (Contributed by RP, 21-Sep-2023)

Ref Expression
Assertion 1no 
|- ( 1o X. { 2o } ) e. No

Proof

Step Hyp Ref Expression
1 1on 
 |-  1o e. On
2 1 onnoi 
 |-  ( 1o X. { 2o } ) e. No