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Mirrors > Home > MPE Home > Th. List > facnn2 | Structured version Visualization version GIF version |
Description: Value of the factorial function expressed recursively. (Contributed by NM, 2-Dec-2004.) |
Ref | Expression |
---|---|
facnn2 | ⊢ (𝑁 ∈ ℕ → (!‘𝑁) = ((!‘(𝑁 − 1)) · 𝑁)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | elnnnn0 11336 | . 2 ⊢ (𝑁 ∈ ℕ ↔ (𝑁 ∈ ℂ ∧ (𝑁 − 1) ∈ ℕ0)) | |
2 | facp1 13065 | . . . 4 ⊢ ((𝑁 − 1) ∈ ℕ0 → (!‘((𝑁 − 1) + 1)) = ((!‘(𝑁 − 1)) · ((𝑁 − 1) + 1))) | |
3 | 2 | adantl 482 | . . 3 ⊢ ((𝑁 ∈ ℂ ∧ (𝑁 − 1) ∈ ℕ0) → (!‘((𝑁 − 1) + 1)) = ((!‘(𝑁 − 1)) · ((𝑁 − 1) + 1))) |
4 | npcan1 10455 | . . . . 5 ⊢ (𝑁 ∈ ℂ → ((𝑁 − 1) + 1) = 𝑁) | |
5 | 4 | fveq2d 6195 | . . . 4 ⊢ (𝑁 ∈ ℂ → (!‘((𝑁 − 1) + 1)) = (!‘𝑁)) |
6 | 5 | adantr 481 | . . 3 ⊢ ((𝑁 ∈ ℂ ∧ (𝑁 − 1) ∈ ℕ0) → (!‘((𝑁 − 1) + 1)) = (!‘𝑁)) |
7 | 4 | oveq2d 6666 | . . . 4 ⊢ (𝑁 ∈ ℂ → ((!‘(𝑁 − 1)) · ((𝑁 − 1) + 1)) = ((!‘(𝑁 − 1)) · 𝑁)) |
8 | 7 | adantr 481 | . . 3 ⊢ ((𝑁 ∈ ℂ ∧ (𝑁 − 1) ∈ ℕ0) → ((!‘(𝑁 − 1)) · ((𝑁 − 1) + 1)) = ((!‘(𝑁 − 1)) · 𝑁)) |
9 | 3, 6, 8 | 3eqtr3d 2664 | . 2 ⊢ ((𝑁 ∈ ℂ ∧ (𝑁 − 1) ∈ ℕ0) → (!‘𝑁) = ((!‘(𝑁 − 1)) · 𝑁)) |
10 | 1, 9 | sylbi 207 | 1 ⊢ (𝑁 ∈ ℕ → (!‘𝑁) = ((!‘(𝑁 − 1)) · 𝑁)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ∧ wa 384 = wceq 1483 ∈ wcel 1990 ‘cfv 5888 (class class class)co 6650 ℂcc 9934 1c1 9937 + caddc 9939 · cmul 9941 − cmin 10266 ℕcn 11020 ℕ0cn0 11292 !cfa 13060 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1722 ax-4 1737 ax-5 1839 ax-6 1888 ax-7 1935 ax-8 1992 ax-9 1999 ax-10 2019 ax-11 2034 ax-12 2047 ax-13 2246 ax-ext 2602 ax-sep 4781 ax-nul 4789 ax-pow 4843 ax-pr 4906 ax-un 6949 ax-cnex 9992 ax-resscn 9993 ax-1cn 9994 ax-icn 9995 ax-addcl 9996 ax-addrcl 9997 ax-mulcl 9998 ax-mulrcl 9999 ax-mulcom 10000 ax-addass 10001 ax-mulass 10002 ax-distr 10003 ax-i2m1 10004 ax-1ne0 10005 ax-1rid 10006 ax-rnegex 10007 ax-rrecex 10008 ax-cnre 10009 ax-pre-lttri 10010 ax-pre-lttrn 10011 ax-pre-ltadd 10012 ax-pre-mulgt0 10013 |
This theorem depends on definitions: df-bi 197 df-or 385 df-an 386 df-3or 1038 df-3an 1039 df-tru 1486 df-ex 1705 df-nf 1710 df-sb 1881 df-eu 2474 df-mo 2475 df-clab 2609 df-cleq 2615 df-clel 2618 df-nfc 2753 df-ne 2795 df-nel 2898 df-ral 2917 df-rex 2918 df-reu 2919 df-rab 2921 df-v 3202 df-sbc 3436 df-csb 3534 df-dif 3577 df-un 3579 df-in 3581 df-ss 3588 df-pss 3590 df-nul 3916 df-if 4087 df-pw 4160 df-sn 4178 df-pr 4180 df-tp 4182 df-op 4184 df-uni 4437 df-iun 4522 df-br 4654 df-opab 4713 df-mpt 4730 df-tr 4753 df-id 5024 df-eprel 5029 df-po 5035 df-so 5036 df-fr 5073 df-we 5075 df-xp 5120 df-rel 5121 df-cnv 5122 df-co 5123 df-dm 5124 df-rn 5125 df-res 5126 df-ima 5127 df-pred 5680 df-ord 5726 df-on 5727 df-lim 5728 df-suc 5729 df-iota 5851 df-fun 5890 df-fn 5891 df-f 5892 df-f1 5893 df-fo 5894 df-f1o 5895 df-fv 5896 df-riota 6611 df-ov 6653 df-oprab 6654 df-mpt2 6655 df-om 7066 df-2nd 7169 df-wrecs 7407 df-recs 7468 df-rdg 7506 df-er 7742 df-en 7956 df-dom 7957 df-sdom 7958 df-pnf 10076 df-mnf 10077 df-xr 10078 df-ltxr 10079 df-le 10080 df-sub 10268 df-neg 10269 df-nn 11021 df-n0 11293 df-z 11378 df-uz 11688 df-seq 12802 df-fac 13061 |
This theorem is referenced by: faclbnd4lem1 13080 bcn1 13100 bcm1k 13102 hashf1 13241 dvdsfac 15048 chtublem 24936 bcmono 25002 dvnxpaek 40157 |
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