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Description: Any set is equinumerous to its cardinal number. Deduction form of cardid . (Contributed by David Moews, 1-May-2017)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | cardidd.1 | ⊢ ( 𝜑 → 𝐴 ∈ 𝐵 ) | |
| Assertion | cardidd | ⊢ ( 𝜑 → ( card ‘ 𝐴 ) ≈ 𝐴 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | cardidd.1 | ⊢ ( 𝜑 → 𝐴 ∈ 𝐵 ) | |
| 2 | cardidg | ⊢ ( 𝐴 ∈ 𝐵 → ( card ‘ 𝐴 ) ≈ 𝐴 ) | |
| 3 | 1 2 | syl | ⊢ ( 𝜑 → ( card ‘ 𝐴 ) ≈ 𝐴 ) |