Description: Two ways to say that A is a nonzero ordinal number. (Contributed by Mario Carneiro, 21-May-2015)
Ref | Expression | ||
---|---|---|---|
Assertion | ondif1 | ⊢ ( 𝐴 ∈ ( On ∖ 1o ) ↔ ( 𝐴 ∈ On ∧ ∅ ∈ 𝐴 ) ) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | dif1o | ⊢ ( 𝐴 ∈ ( On ∖ 1o ) ↔ ( 𝐴 ∈ On ∧ 𝐴 ≠ ∅ ) ) | |
2 | on0eln0 | ⊢ ( 𝐴 ∈ On → ( ∅ ∈ 𝐴 ↔ 𝐴 ≠ ∅ ) ) | |
3 | 2 | pm5.32i | ⊢ ( ( 𝐴 ∈ On ∧ ∅ ∈ 𝐴 ) ↔ ( 𝐴 ∈ On ∧ 𝐴 ≠ ∅ ) ) |
4 | 1 3 | bitr4i | ⊢ ( 𝐴 ∈ ( On ∖ 1o ) ↔ ( 𝐴 ∈ On ∧ ∅ ∈ 𝐴 ) ) |