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| Mirrors > Home > MPE Home > Th. List > nn0ge2m1nn | Structured version Visualization version GIF version | ||
| Description: If a nonnegative integer is greater than or equal to two, the integer decreased by 1 is a positive integer. (Contributed by Alexander van der Vekens, 1-Aug-2018.) (Revised by AV, 4-Jan-2020.) | 
| Ref | Expression | 
|---|---|
| nn0ge2m1nn | ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → (𝑁 − 1) ∈ ℕ) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | simpl 482 | . . . 4 ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → 𝑁 ∈ ℕ0) | |
| 2 | 1red 11262 | . . . . . . 7 ⊢ (𝑁 ∈ ℕ0 → 1 ∈ ℝ) | |
| 3 | 2re 12340 | . . . . . . . 8 ⊢ 2 ∈ ℝ | |
| 4 | 3 | a1i 11 | . . . . . . 7 ⊢ (𝑁 ∈ ℕ0 → 2 ∈ ℝ) | 
| 5 | nn0re 12535 | . . . . . . 7 ⊢ (𝑁 ∈ ℕ0 → 𝑁 ∈ ℝ) | |
| 6 | 2, 4, 5 | 3jca 1129 | . . . . . 6 ⊢ (𝑁 ∈ ℕ0 → (1 ∈ ℝ ∧ 2 ∈ ℝ ∧ 𝑁 ∈ ℝ)) | 
| 7 | 6 | adantr 480 | . . . . 5 ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → (1 ∈ ℝ ∧ 2 ∈ ℝ ∧ 𝑁 ∈ ℝ)) | 
| 8 | simpr 484 | . . . . . 6 ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → 2 ≤ 𝑁) | |
| 9 | 1lt2 12437 | . . . . . 6 ⊢ 1 < 2 | |
| 10 | 8, 9 | jctil 519 | . . . . 5 ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → (1 < 2 ∧ 2 ≤ 𝑁)) | 
| 11 | ltleletr 11354 | . . . . 5 ⊢ ((1 ∈ ℝ ∧ 2 ∈ ℝ ∧ 𝑁 ∈ ℝ) → ((1 < 2 ∧ 2 ≤ 𝑁) → 1 ≤ 𝑁)) | |
| 12 | 7, 10, 11 | sylc 65 | . . . 4 ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → 1 ≤ 𝑁) | 
| 13 | elnnnn0c 12571 | . . . 4 ⊢ (𝑁 ∈ ℕ ↔ (𝑁 ∈ ℕ0 ∧ 1 ≤ 𝑁)) | |
| 14 | 1, 12, 13 | sylanbrc 583 | . . 3 ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → 𝑁 ∈ ℕ) | 
| 15 | nn1m1nn 12287 | . . 3 ⊢ (𝑁 ∈ ℕ → (𝑁 = 1 ∨ (𝑁 − 1) ∈ ℕ)) | |
| 16 | 14, 15 | syl 17 | . 2 ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → (𝑁 = 1 ∨ (𝑁 − 1) ∈ ℕ)) | 
| 17 | breq2 5147 | . . . . 5 ⊢ (𝑁 = 1 → (2 ≤ 𝑁 ↔ 2 ≤ 1)) | |
| 18 | 1re 11261 | . . . . . . . 8 ⊢ 1 ∈ ℝ | |
| 19 | 18, 3 | ltnlei 11382 | . . . . . . 7 ⊢ (1 < 2 ↔ ¬ 2 ≤ 1) | 
| 20 | pm2.21 123 | . . . . . . 7 ⊢ (¬ 2 ≤ 1 → (2 ≤ 1 → (𝑁 − 1) ∈ ℕ)) | |
| 21 | 19, 20 | sylbi 217 | . . . . . 6 ⊢ (1 < 2 → (2 ≤ 1 → (𝑁 − 1) ∈ ℕ)) | 
| 22 | 9, 21 | ax-mp 5 | . . . . 5 ⊢ (2 ≤ 1 → (𝑁 − 1) ∈ ℕ) | 
| 23 | 17, 22 | biimtrdi 253 | . . . 4 ⊢ (𝑁 = 1 → (2 ≤ 𝑁 → (𝑁 − 1) ∈ ℕ)) | 
| 24 | 23 | adantld 490 | . . 3 ⊢ (𝑁 = 1 → ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → (𝑁 − 1) ∈ ℕ)) | 
| 25 | ax-1 6 | . . 3 ⊢ ((𝑁 − 1) ∈ ℕ → ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → (𝑁 − 1) ∈ ℕ)) | |
| 26 | 24, 25 | jaoi 858 | . 2 ⊢ ((𝑁 = 1 ∨ (𝑁 − 1) ∈ ℕ) → ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → (𝑁 − 1) ∈ ℕ)) | 
| 27 | 16, 26 | mpcom 38 | 1 ⊢ ((𝑁 ∈ ℕ0 ∧ 2 ≤ 𝑁) → (𝑁 − 1) ∈ ℕ) | 
| Colors of variables: wff setvar class | 
| Syntax hints: ¬ wn 3 → wi 4 ∧ wa 395 ∨ wo 848 ∧ w3a 1087 = wceq 1540 ∈ wcel 2108 class class class wbr 5143 (class class class)co 7431 ℝcr 11154 1c1 11156 < clt 11295 ≤ cle 11296 − cmin 11492 ℕcn 12266 2c2 12321 ℕ0cn0 12526 | 
| This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1795 ax-4 1809 ax-5 1910 ax-6 1967 ax-7 2007 ax-8 2110 ax-9 2118 ax-10 2141 ax-11 2157 ax-12 2177 ax-ext 2708 ax-sep 5296 ax-nul 5306 ax-pow 5365 ax-pr 5432 ax-un 7755 ax-resscn 11212 ax-1cn 11213 ax-icn 11214 ax-addcl 11215 ax-addrcl 11216 ax-mulcl 11217 ax-mulrcl 11218 ax-mulcom 11219 ax-addass 11220 ax-mulass 11221 ax-distr 11222 ax-i2m1 11223 ax-1ne0 11224 ax-1rid 11225 ax-rnegex 11226 ax-rrecex 11227 ax-cnre 11228 ax-pre-lttri 11229 ax-pre-lttrn 11230 ax-pre-ltadd 11231 ax-pre-mulgt0 11232 | 
| This theorem depends on definitions: df-bi 207 df-an 396 df-or 849 df-3or 1088 df-3an 1089 df-tru 1543 df-fal 1553 df-ex 1780 df-nf 1784 df-sb 2065 df-mo 2540 df-eu 2569 df-clab 2715 df-cleq 2729 df-clel 2816 df-nfc 2892 df-ne 2941 df-nel 3047 df-ral 3062 df-rex 3071 df-reu 3381 df-rab 3437 df-v 3482 df-sbc 3789 df-csb 3900 df-dif 3954 df-un 3956 df-in 3958 df-ss 3968 df-pss 3971 df-nul 4334 df-if 4526 df-pw 4602 df-sn 4627 df-pr 4629 df-op 4633 df-uni 4908 df-iun 4993 df-br 5144 df-opab 5206 df-mpt 5226 df-tr 5260 df-id 5578 df-eprel 5584 df-po 5592 df-so 5593 df-fr 5637 df-we 5639 df-xp 5691 df-rel 5692 df-cnv 5693 df-co 5694 df-dm 5695 df-rn 5696 df-res 5697 df-ima 5698 df-pred 6321 df-ord 6387 df-on 6388 df-lim 6389 df-suc 6390 df-iota 6514 df-fun 6563 df-fn 6564 df-f 6565 df-f1 6566 df-fo 6567 df-f1o 6568 df-fv 6569 df-riota 7388 df-ov 7434 df-oprab 7435 df-mpo 7436 df-om 7888 df-2nd 8015 df-frecs 8306 df-wrecs 8337 df-recs 8411 df-rdg 8450 df-er 8745 df-en 8986 df-dom 8987 df-sdom 8988 df-pnf 11297 df-mnf 11298 df-xr 11299 df-ltxr 11300 df-le 11301 df-sub 11494 df-neg 11495 df-nn 12267 df-2 12329 df-n0 12527 | 
| This theorem is referenced by: nn0ge2m1nn0 12597 wwlksm1edg 29901 clwlkclwwlklem2fv2 30015 clwlkclwwlk 30021 pfxlsw2ccat 32935 fmtnoprmfac1 47552 logbpw2m1 48488 blenpw2m1 48500 nnolog2flm1 48511 | 
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