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Mirrors > Home > MPE Home > Th. List > bcn2m1 | Structured version Visualization version GIF version |
Description: Compute the binomial coefficient "𝑁 choose 2 " from "(𝑁 − 1) choose 2 ": (N-1) + ( (N-1) 2 ) = ( N 2 ). (Contributed by Alexander van der Vekens, 7-Jan-2018.) |
Ref | Expression |
---|---|
bcn2m1 | ⊢ (𝑁 ∈ ℕ → ((𝑁 − 1) + ((𝑁 − 1)C2)) = (𝑁C2)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nnm1nn0 11926 | . . . 4 ⊢ (𝑁 ∈ ℕ → (𝑁 − 1) ∈ ℕ0) | |
2 | 1 | nn0cnd 11945 | . . 3 ⊢ (𝑁 ∈ ℕ → (𝑁 − 1) ∈ ℂ) |
3 | 2z 12002 | . . . . 5 ⊢ 2 ∈ ℤ | |
4 | bccl 13670 | . . . . 5 ⊢ (((𝑁 − 1) ∈ ℕ0 ∧ 2 ∈ ℤ) → ((𝑁 − 1)C2) ∈ ℕ0) | |
5 | 1, 3, 4 | sylancl 586 | . . . 4 ⊢ (𝑁 ∈ ℕ → ((𝑁 − 1)C2) ∈ ℕ0) |
6 | 5 | nn0cnd 11945 | . . 3 ⊢ (𝑁 ∈ ℕ → ((𝑁 − 1)C2) ∈ ℂ) |
7 | 2, 6 | addcomd 10830 | . 2 ⊢ (𝑁 ∈ ℕ → ((𝑁 − 1) + ((𝑁 − 1)C2)) = (((𝑁 − 1)C2) + (𝑁 − 1))) |
8 | bcn1 13661 | . . . . . 6 ⊢ ((𝑁 − 1) ∈ ℕ0 → ((𝑁 − 1)C1) = (𝑁 − 1)) | |
9 | 8 | eqcomd 2824 | . . . . 5 ⊢ ((𝑁 − 1) ∈ ℕ0 → (𝑁 − 1) = ((𝑁 − 1)C1)) |
10 | 1, 9 | syl 17 | . . . 4 ⊢ (𝑁 ∈ ℕ → (𝑁 − 1) = ((𝑁 − 1)C1)) |
11 | 1e2m1 11752 | . . . . . 6 ⊢ 1 = (2 − 1) | |
12 | 11 | a1i 11 | . . . . 5 ⊢ (𝑁 ∈ ℕ → 1 = (2 − 1)) |
13 | 12 | oveq2d 7161 | . . . 4 ⊢ (𝑁 ∈ ℕ → ((𝑁 − 1)C1) = ((𝑁 − 1)C(2 − 1))) |
14 | 10, 13 | eqtrd 2853 | . . 3 ⊢ (𝑁 ∈ ℕ → (𝑁 − 1) = ((𝑁 − 1)C(2 − 1))) |
15 | 14 | oveq2d 7161 | . 2 ⊢ (𝑁 ∈ ℕ → (((𝑁 − 1)C2) + (𝑁 − 1)) = (((𝑁 − 1)C2) + ((𝑁 − 1)C(2 − 1)))) |
16 | bcpasc 13669 | . . . 4 ⊢ (((𝑁 − 1) ∈ ℕ0 ∧ 2 ∈ ℤ) → (((𝑁 − 1)C2) + ((𝑁 − 1)C(2 − 1))) = (((𝑁 − 1) + 1)C2)) | |
17 | 1, 3, 16 | sylancl 586 | . . 3 ⊢ (𝑁 ∈ ℕ → (((𝑁 − 1)C2) + ((𝑁 − 1)C(2 − 1))) = (((𝑁 − 1) + 1)C2)) |
18 | nncn 11634 | . . . . 5 ⊢ (𝑁 ∈ ℕ → 𝑁 ∈ ℂ) | |
19 | 1cnd 10624 | . . . . 5 ⊢ (𝑁 ∈ ℕ → 1 ∈ ℂ) | |
20 | 18, 19 | npcand 10989 | . . . 4 ⊢ (𝑁 ∈ ℕ → ((𝑁 − 1) + 1) = 𝑁) |
21 | 20 | oveq1d 7160 | . . 3 ⊢ (𝑁 ∈ ℕ → (((𝑁 − 1) + 1)C2) = (𝑁C2)) |
22 | 17, 21 | eqtrd 2853 | . 2 ⊢ (𝑁 ∈ ℕ → (((𝑁 − 1)C2) + ((𝑁 − 1)C(2 − 1))) = (𝑁C2)) |
23 | 7, 15, 22 | 3eqtrd 2857 | 1 ⊢ (𝑁 ∈ ℕ → ((𝑁 − 1) + ((𝑁 − 1)C2)) = (𝑁C2)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 = wceq 1528 ∈ wcel 2105 (class class class)co 7145 1c1 10526 + caddc 10528 − cmin 10858 ℕcn 11626 2c2 11680 ℕ0cn0 11885 ℤcz 11969 Ccbc 13650 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1787 ax-4 1801 ax-5 1902 ax-6 1961 ax-7 2006 ax-8 2107 ax-9 2115 ax-10 2136 ax-11 2151 ax-12 2167 ax-ext 2790 ax-sep 5194 ax-nul 5201 ax-pow 5257 ax-pr 5320 ax-un 7450 ax-cnex 10581 ax-resscn 10582 ax-1cn 10583 ax-icn 10584 ax-addcl 10585 ax-addrcl 10586 ax-mulcl 10587 ax-mulrcl 10588 ax-mulcom 10589 ax-addass 10590 ax-mulass 10591 ax-distr 10592 ax-i2m1 10593 ax-1ne0 10594 ax-1rid 10595 ax-rnegex 10596 ax-rrecex 10597 ax-cnre 10598 ax-pre-lttri 10599 ax-pre-lttrn 10600 ax-pre-ltadd 10601 ax-pre-mulgt0 10602 |
This theorem depends on definitions: df-bi 208 df-an 397 df-or 842 df-3or 1080 df-3an 1081 df-tru 1531 df-ex 1772 df-nf 1776 df-sb 2061 df-mo 2615 df-eu 2647 df-clab 2797 df-cleq 2811 df-clel 2890 df-nfc 2960 df-ne 3014 df-nel 3121 df-ral 3140 df-rex 3141 df-reu 3142 df-rmo 3143 df-rab 3144 df-v 3494 df-sbc 3770 df-csb 3881 df-dif 3936 df-un 3938 df-in 3940 df-ss 3949 df-pss 3951 df-nul 4289 df-if 4464 df-pw 4537 df-sn 4558 df-pr 4560 df-tp 4562 df-op 4564 df-uni 4831 df-iun 4912 df-br 5058 df-opab 5120 df-mpt 5138 df-tr 5164 df-id 5453 df-eprel 5458 df-po 5467 df-so 5468 df-fr 5507 df-we 5509 df-xp 5554 df-rel 5555 df-cnv 5556 df-co 5557 df-dm 5558 df-rn 5559 df-res 5560 df-ima 5561 df-pred 6141 df-ord 6187 df-on 6188 df-lim 6189 df-suc 6190 df-iota 6307 df-fun 6350 df-fn 6351 df-f 6352 df-f1 6353 df-fo 6354 df-f1o 6355 df-fv 6356 df-riota 7103 df-ov 7148 df-oprab 7149 df-mpo 7150 df-om 7570 df-1st 7678 df-2nd 7679 df-wrecs 7936 df-recs 7997 df-rdg 8035 df-er 8278 df-en 8498 df-dom 8499 df-sdom 8500 df-pnf 10665 df-mnf 10666 df-xr 10667 df-ltxr 10668 df-le 10669 df-sub 10860 df-neg 10861 df-div 11286 df-nn 11627 df-2 11688 df-n0 11886 df-z 11970 df-uz 12232 df-rp 12378 df-fz 12881 df-seq 13358 df-fac 13622 df-bc 13651 |
This theorem is referenced by: cusgrsize2inds 27162 |
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