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Mirrors > Home > ILE Home > Th. List > op1st | GIF version |
Description: Extract the first member of an ordered pair. (Contributed by NM, 5-Oct-2004.) |
Ref | Expression |
---|---|
op1st.1 | ⊢ 𝐴 ∈ V |
op1st.2 | ⊢ 𝐵 ∈ V |
Ref | Expression |
---|---|
op1st | ⊢ (1st ‘⟨𝐴, 𝐵⟩) = 𝐴 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | op1st.1 | . . . 4 ⊢ 𝐴 ∈ V | |
2 | op1st.2 | . . . 4 ⊢ 𝐵 ∈ V | |
3 | opexg 4228 | . . . 4 ⊢ ((𝐴 ∈ V ∧ 𝐵 ∈ V) → ⟨𝐴, 𝐵⟩ ∈ V) | |
4 | 1, 2, 3 | mp2an 426 | . . 3 ⊢ ⟨𝐴, 𝐵⟩ ∈ V |
5 | 1stvalg 6142 | . . 3 ⊢ (⟨𝐴, 𝐵⟩ ∈ V → (1st ‘⟨𝐴, 𝐵⟩) = ∪ dom {⟨𝐴, 𝐵⟩}) | |
6 | 4, 5 | ax-mp 5 | . 2 ⊢ (1st ‘⟨𝐴, 𝐵⟩) = ∪ dom {⟨𝐴, 𝐵⟩} |
7 | 1, 2 | op1sta 5110 | . 2 ⊢ ∪ dom {⟨𝐴, 𝐵⟩} = 𝐴 |
8 | 6, 7 | eqtri 2198 | 1 ⊢ (1st ‘⟨𝐴, 𝐵⟩) = 𝐴 |
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