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Mirrors > Home > MPE Home > Th. List > hashdifpr | Structured version Visualization version GIF version |
Description: The size of the difference of a finite set and a proper pair of its elements is the set's size minus 2. (Contributed by AV, 16-Dec-2020.) |
Ref | Expression |
---|---|
hashdifpr | ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → (♯‘(𝐴 ∖ {𝐵, 𝐶})) = ((♯‘𝐴) − 2)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | difpr 4691 | . . . 4 ⊢ (𝐴 ∖ {𝐵, 𝐶}) = ((𝐴 ∖ {𝐵}) ∖ {𝐶}) | |
2 | 1 | a1i 11 | . . 3 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → (𝐴 ∖ {𝐵, 𝐶}) = ((𝐴 ∖ {𝐵}) ∖ {𝐶})) |
3 | 2 | fveq2d 6678 | . 2 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → (♯‘(𝐴 ∖ {𝐵, 𝐶})) = (♯‘((𝐴 ∖ {𝐵}) ∖ {𝐶}))) |
4 | diffi 8827 | . . 3 ⊢ (𝐴 ∈ Fin → (𝐴 ∖ {𝐵}) ∈ Fin) | |
5 | necom 2987 | . . . . . . . 8 ⊢ (𝐵 ≠ 𝐶 ↔ 𝐶 ≠ 𝐵) | |
6 | 5 | biimpi 219 | . . . . . . 7 ⊢ (𝐵 ≠ 𝐶 → 𝐶 ≠ 𝐵) |
7 | 6 | anim2i 620 | . . . . . 6 ⊢ ((𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶) → (𝐶 ∈ 𝐴 ∧ 𝐶 ≠ 𝐵)) |
8 | 7 | 3adant1 1131 | . . . . 5 ⊢ ((𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶) → (𝐶 ∈ 𝐴 ∧ 𝐶 ≠ 𝐵)) |
9 | 8 | adantl 485 | . . . 4 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → (𝐶 ∈ 𝐴 ∧ 𝐶 ≠ 𝐵)) |
10 | eldifsn 4675 | . . . 4 ⊢ (𝐶 ∈ (𝐴 ∖ {𝐵}) ↔ (𝐶 ∈ 𝐴 ∧ 𝐶 ≠ 𝐵)) | |
11 | 9, 10 | sylibr 237 | . . 3 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → 𝐶 ∈ (𝐴 ∖ {𝐵})) |
12 | hashdifsn 13867 | . . 3 ⊢ (((𝐴 ∖ {𝐵}) ∈ Fin ∧ 𝐶 ∈ (𝐴 ∖ {𝐵})) → (♯‘((𝐴 ∖ {𝐵}) ∖ {𝐶})) = ((♯‘(𝐴 ∖ {𝐵})) − 1)) | |
13 | 4, 11, 12 | syl2an2r 685 | . 2 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → (♯‘((𝐴 ∖ {𝐵}) ∖ {𝐶})) = ((♯‘(𝐴 ∖ {𝐵})) − 1)) |
14 | hashdifsn 13867 | . . . . 5 ⊢ ((𝐴 ∈ Fin ∧ 𝐵 ∈ 𝐴) → (♯‘(𝐴 ∖ {𝐵})) = ((♯‘𝐴) − 1)) | |
15 | 14 | 3ad2antr1 1189 | . . . 4 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → (♯‘(𝐴 ∖ {𝐵})) = ((♯‘𝐴) − 1)) |
16 | 15 | oveq1d 7185 | . . 3 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → ((♯‘(𝐴 ∖ {𝐵})) − 1) = (((♯‘𝐴) − 1) − 1)) |
17 | hashcl 13809 | . . . . . 6 ⊢ (𝐴 ∈ Fin → (♯‘𝐴) ∈ ℕ0) | |
18 | 17 | nn0cnd 12038 | . . . . 5 ⊢ (𝐴 ∈ Fin → (♯‘𝐴) ∈ ℂ) |
19 | sub1m1 11968 | . . . . 5 ⊢ ((♯‘𝐴) ∈ ℂ → (((♯‘𝐴) − 1) − 1) = ((♯‘𝐴) − 2)) | |
20 | 18, 19 | syl 17 | . . . 4 ⊢ (𝐴 ∈ Fin → (((♯‘𝐴) − 1) − 1) = ((♯‘𝐴) − 2)) |
21 | 20 | adantr 484 | . . 3 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → (((♯‘𝐴) − 1) − 1) = ((♯‘𝐴) − 2)) |
22 | 16, 21 | eqtrd 2773 | . 2 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → ((♯‘(𝐴 ∖ {𝐵})) − 1) = ((♯‘𝐴) − 2)) |
23 | 3, 13, 22 | 3eqtrd 2777 | 1 ⊢ ((𝐴 ∈ Fin ∧ (𝐵 ∈ 𝐴 ∧ 𝐶 ∈ 𝐴 ∧ 𝐵 ≠ 𝐶)) → (♯‘(𝐴 ∖ {𝐵, 𝐶})) = ((♯‘𝐴) − 2)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 399 ∧ w3a 1088 = wceq 1542 ∈ wcel 2114 ≠ wne 2934 ∖ cdif 3840 {csn 4516 {cpr 4518 ‘cfv 6339 (class class class)co 7170 Fincfn 8555 ℂcc 10613 1c1 10616 − cmin 10948 2c2 11771 ♯chash 13782 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1802 ax-4 1816 ax-5 1917 ax-6 1975 ax-7 2020 ax-8 2116 ax-9 2124 ax-10 2145 ax-11 2162 ax-12 2179 ax-ext 2710 ax-sep 5167 ax-nul 5174 ax-pow 5232 ax-pr 5296 ax-un 7479 ax-cnex 10671 ax-resscn 10672 ax-1cn 10673 ax-icn 10674 ax-addcl 10675 ax-addrcl 10676 ax-mulcl 10677 ax-mulrcl 10678 ax-mulcom 10679 ax-addass 10680 ax-mulass 10681 ax-distr 10682 ax-i2m1 10683 ax-1ne0 10684 ax-1rid 10685 ax-rnegex 10686 ax-rrecex 10687 ax-cnre 10688 ax-pre-lttri 10689 ax-pre-lttrn 10690 ax-pre-ltadd 10691 ax-pre-mulgt0 10692 |
This theorem depends on definitions: df-bi 210 df-an 400 df-or 847 df-3or 1089 df-3an 1090 df-tru 1545 df-fal 1555 df-ex 1787 df-nf 1791 df-sb 2075 df-mo 2540 df-eu 2570 df-clab 2717 df-cleq 2730 df-clel 2811 df-nfc 2881 df-ne 2935 df-nel 3039 df-ral 3058 df-rex 3059 df-reu 3060 df-rab 3062 df-v 3400 df-sbc 3681 df-csb 3791 df-dif 3846 df-un 3848 df-in 3850 df-ss 3860 df-pss 3862 df-nul 4212 df-if 4415 df-pw 4490 df-sn 4517 df-pr 4519 df-tp 4521 df-op 4523 df-uni 4797 df-int 4837 df-iun 4883 df-br 5031 df-opab 5093 df-mpt 5111 df-tr 5137 df-id 5429 df-eprel 5434 df-po 5442 df-so 5443 df-fr 5483 df-we 5485 df-xp 5531 df-rel 5532 df-cnv 5533 df-co 5534 df-dm 5535 df-rn 5536 df-res 5537 df-ima 5538 df-pred 6129 df-ord 6175 df-on 6176 df-lim 6177 df-suc 6178 df-iota 6297 df-fun 6341 df-fn 6342 df-f 6343 df-f1 6344 df-fo 6345 df-f1o 6346 df-fv 6347 df-riota 7127 df-ov 7173 df-oprab 7174 df-mpo 7175 df-om 7600 df-1st 7714 df-2nd 7715 df-wrecs 7976 df-recs 8037 df-rdg 8075 df-1o 8131 df-oadd 8135 df-er 8320 df-en 8556 df-dom 8557 df-sdom 8558 df-fin 8559 df-dju 9403 df-card 9441 df-pnf 10755 df-mnf 10756 df-xr 10757 df-ltxr 10758 df-le 10759 df-sub 10950 df-neg 10951 df-nn 11717 df-2 11779 df-n0 11977 df-z 12063 df-uz 12325 df-fz 12982 df-hash 13783 |
This theorem is referenced by: nbfusgrlevtxm2 27320 |
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