Description: The double converse of a function is a function. (Contributed by NM, 21-Sep-2004)
Ref | Expression | ||
---|---|---|---|
Assertion | funcnvcnv | ⊢ ( Fun 𝐴 → Fun ◡ ◡ 𝐴 ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | cnvcnvss | ⊢ ◡ ◡ 𝐴 ⊆ 𝐴 | |
2 | funss | ⊢ ( ◡ ◡ 𝐴 ⊆ 𝐴 → ( Fun 𝐴 → Fun ◡ ◡ 𝐴 ) ) | |
3 | 1 2 | ax-mp | ⊢ ( Fun 𝐴 → Fun ◡ ◡ 𝐴 ) |