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Mirrors > Home > MPE Home > Th. List > cardsn | Structured version Visualization version GIF version |
Description: A singleton has cardinality one. (Contributed by Mario Carneiro, 10-Jan-2013.) |
Ref | Expression |
---|---|
cardsn | ⊢ (𝐴 ∈ 𝑉 → (card‘{𝐴}) = 1o) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqid 2735 | . . 3 ⊢ {𝐴} = {𝐴} | |
2 | sneq 4641 | . . . . 5 ⊢ (𝑥 = 𝐴 → {𝑥} = {𝐴}) | |
3 | 2 | eqeq2d 2746 | . . . 4 ⊢ (𝑥 = 𝐴 → ({𝐴} = {𝑥} ↔ {𝐴} = {𝐴})) |
4 | 3 | spcegv 3597 | . . 3 ⊢ (𝐴 ∈ 𝑉 → ({𝐴} = {𝐴} → ∃𝑥{𝐴} = {𝑥})) |
5 | 1, 4 | mpi 20 | . 2 ⊢ (𝐴 ∈ 𝑉 → ∃𝑥{𝐴} = {𝑥}) |
6 | card1 10006 | . 2 ⊢ ((card‘{𝐴}) = 1o ↔ ∃𝑥{𝐴} = {𝑥}) | |
7 | 5, 6 | sylibr 234 | 1 ⊢ (𝐴 ∈ 𝑉 → (card‘{𝐴}) = 1o) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 = wceq 1537 ∃wex 1776 ∈ wcel 2106 {csn 4631 ‘cfv 6563 1oc1o 8498 cardccrd 9973 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1792 ax-4 1806 ax-5 1908 ax-6 1965 ax-7 2005 ax-8 2108 ax-9 2116 ax-10 2139 ax-11 2155 ax-12 2175 ax-ext 2706 ax-sep 5302 ax-nul 5312 ax-pow 5371 ax-pr 5438 ax-un 7754 |
This theorem depends on definitions: df-bi 207 df-an 396 df-or 848 df-3or 1087 df-3an 1088 df-tru 1540 df-fal 1550 df-ex 1777 df-nf 1781 df-sb 2063 df-mo 2538 df-eu 2567 df-clab 2713 df-cleq 2727 df-clel 2814 df-nfc 2890 df-ne 2939 df-ral 3060 df-rex 3069 df-reu 3379 df-rab 3434 df-v 3480 df-sbc 3792 df-csb 3909 df-dif 3966 df-un 3968 df-in 3970 df-ss 3980 df-pss 3983 df-nul 4340 df-if 4532 df-pw 4607 df-sn 4632 df-pr 4634 df-op 4638 df-uni 4913 df-int 4952 df-br 5149 df-opab 5211 df-mpt 5232 df-tr 5266 df-id 5583 df-eprel 5589 df-po 5597 df-so 5598 df-fr 5641 df-we 5643 df-xp 5695 df-rel 5696 df-cnv 5697 df-co 5698 df-dm 5699 df-rn 5700 df-res 5701 df-ima 5702 df-ord 6389 df-on 6390 df-lim 6391 df-suc 6392 df-iota 6516 df-fun 6565 df-fn 6566 df-f 6567 df-f1 6568 df-fo 6569 df-f1o 6570 df-fv 6571 df-om 7888 df-1o 8505 df-er 8744 df-en 8985 df-dom 8986 df-sdom 8987 df-fin 8988 df-card 9977 |
This theorem is referenced by: ackbij1lem14 10270 cfsuc 10295 |
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