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 ) |