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Mirrors > Home > MPE Home > Th. List > incom | Structured version Visualization version GIF version |
Description: Commutative law for intersection of classes. Exercise 7 of [TakeutiZaring] p. 17. (Contributed by NM, 21-Jun-1993.) (Proof shortened by SN, 12-Dec-2023.) |
Ref | Expression |
---|---|
incom | ⊢ (𝐴 ∩ 𝐵) = (𝐵 ∩ 𝐴) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | rabswap 3413 | . 2 ⊢ {𝑥 ∈ 𝐴 ∣ 𝑥 ∈ 𝐵} = {𝑥 ∈ 𝐵 ∣ 𝑥 ∈ 𝐴} | |
2 | dfin5 3891 | . 2 ⊢ (𝐴 ∩ 𝐵) = {𝑥 ∈ 𝐴 ∣ 𝑥 ∈ 𝐵} | |
3 | dfin5 3891 | . 2 ⊢ (𝐵 ∩ 𝐴) = {𝑥 ∈ 𝐵 ∣ 𝑥 ∈ 𝐴} | |
4 | 1, 2, 3 | 3eqtr4i 2776 | 1 ⊢ (𝐴 ∩ 𝐵) = (𝐵 ∩ 𝐴) |
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