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Mirrors > Home > MPE Home > Th. List > evennn2n | Structured version Visualization version GIF version |
Description: A positive integer is even iff it is twice another positive integer. (Contributed by AV, 12-Aug-2021.) |
Ref | Expression |
---|---|
evennn2n | ⊢ (𝑁 ∈ ℕ → (2 ∥ 𝑁 ↔ ∃𝑛 ∈ ℕ (2 · 𝑛) = 𝑁)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eleq1 2676 | . . . . . . . 8 ⊢ ((2 · 𝑛) = 𝑁 → ((2 · 𝑛) ∈ ℕ ↔ 𝑁 ∈ ℕ)) | |
2 | simpr 476 | . . . . . . . . . 10 ⊢ (((2 · 𝑛) ∈ ℕ ∧ 𝑛 ∈ ℤ) → 𝑛 ∈ ℤ) | |
3 | 2re 10967 | . . . . . . . . . . . 12 ⊢ 2 ∈ ℝ | |
4 | 3 | a1i 11 | . . . . . . . . . . 11 ⊢ (((2 · 𝑛) ∈ ℕ ∧ 𝑛 ∈ ℤ) → 2 ∈ ℝ) |
5 | zre 11258 | . . . . . . . . . . . 12 ⊢ (𝑛 ∈ ℤ → 𝑛 ∈ ℝ) | |
6 | 5 | adantl 481 | . . . . . . . . . . 11 ⊢ (((2 · 𝑛) ∈ ℕ ∧ 𝑛 ∈ ℤ) → 𝑛 ∈ ℝ) |
7 | 0le2 10988 | . . . . . . . . . . . 12 ⊢ 0 ≤ 2 | |
8 | 7 | a1i 11 | . . . . . . . . . . 11 ⊢ (((2 · 𝑛) ∈ ℕ ∧ 𝑛 ∈ ℤ) → 0 ≤ 2) |
9 | nngt0 10926 | . . . . . . . . . . . 12 ⊢ ((2 · 𝑛) ∈ ℕ → 0 < (2 · 𝑛)) | |
10 | 9 | adantr 480 | . . . . . . . . . . 11 ⊢ (((2 · 𝑛) ∈ ℕ ∧ 𝑛 ∈ ℤ) → 0 < (2 · 𝑛)) |
11 | prodgt0 10747 | . . . . . . . . . . 11 ⊢ (((2 ∈ ℝ ∧ 𝑛 ∈ ℝ) ∧ (0 ≤ 2 ∧ 0 < (2 · 𝑛))) → 0 < 𝑛) | |
12 | 4, 6, 8, 10, 11 | syl22anc 1319 | . . . . . . . . . 10 ⊢ (((2 · 𝑛) ∈ ℕ ∧ 𝑛 ∈ ℤ) → 0 < 𝑛) |
13 | elnnz 11264 | . . . . . . . . . 10 ⊢ (𝑛 ∈ ℕ ↔ (𝑛 ∈ ℤ ∧ 0 < 𝑛)) | |
14 | 2, 12, 13 | sylanbrc 695 | . . . . . . . . 9 ⊢ (((2 · 𝑛) ∈ ℕ ∧ 𝑛 ∈ ℤ) → 𝑛 ∈ ℕ) |
15 | 14 | ex 449 | . . . . . . . 8 ⊢ ((2 · 𝑛) ∈ ℕ → (𝑛 ∈ ℤ → 𝑛 ∈ ℕ)) |
16 | 1, 15 | syl6bir 243 | . . . . . . 7 ⊢ ((2 · 𝑛) = 𝑁 → (𝑁 ∈ ℕ → (𝑛 ∈ ℤ → 𝑛 ∈ ℕ))) |
17 | 16 | com13 86 | . . . . . 6 ⊢ (𝑛 ∈ ℤ → (𝑁 ∈ ℕ → ((2 · 𝑛) = 𝑁 → 𝑛 ∈ ℕ))) |
18 | 17 | impcom 445 | . . . . 5 ⊢ ((𝑁 ∈ ℕ ∧ 𝑛 ∈ ℤ) → ((2 · 𝑛) = 𝑁 → 𝑛 ∈ ℕ)) |
19 | 18 | pm4.71rd 665 | . . . 4 ⊢ ((𝑁 ∈ ℕ ∧ 𝑛 ∈ ℤ) → ((2 · 𝑛) = 𝑁 ↔ (𝑛 ∈ ℕ ∧ (2 · 𝑛) = 𝑁))) |
20 | 19 | bicomd 212 | . . 3 ⊢ ((𝑁 ∈ ℕ ∧ 𝑛 ∈ ℤ) → ((𝑛 ∈ ℕ ∧ (2 · 𝑛) = 𝑁) ↔ (2 · 𝑛) = 𝑁)) |
21 | 20 | rexbidva 3031 | . 2 ⊢ (𝑁 ∈ ℕ → (∃𝑛 ∈ ℤ (𝑛 ∈ ℕ ∧ (2 · 𝑛) = 𝑁) ↔ ∃𝑛 ∈ ℤ (2 · 𝑛) = 𝑁)) |
22 | nnssz 11274 | . . 3 ⊢ ℕ ⊆ ℤ | |
23 | rexss 3632 | . . 3 ⊢ (ℕ ⊆ ℤ → (∃𝑛 ∈ ℕ (2 · 𝑛) = 𝑁 ↔ ∃𝑛 ∈ ℤ (𝑛 ∈ ℕ ∧ (2 · 𝑛) = 𝑁))) | |
24 | 22, 23 | mp1i 13 | . 2 ⊢ (𝑁 ∈ ℕ → (∃𝑛 ∈ ℕ (2 · 𝑛) = 𝑁 ↔ ∃𝑛 ∈ ℤ (𝑛 ∈ ℕ ∧ (2 · 𝑛) = 𝑁))) |
25 | even2n 14904 | . . 3 ⊢ (2 ∥ 𝑁 ↔ ∃𝑛 ∈ ℤ (2 · 𝑛) = 𝑁) | |
26 | 25 | a1i 11 | . 2 ⊢ (𝑁 ∈ ℕ → (2 ∥ 𝑁 ↔ ∃𝑛 ∈ ℤ (2 · 𝑛) = 𝑁)) |
27 | 21, 24, 26 | 3bitr4rd 300 | 1 ⊢ (𝑁 ∈ ℕ → (2 ∥ 𝑁 ↔ ∃𝑛 ∈ ℕ (2 · 𝑛) = 𝑁)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 195 ∧ wa 383 = wceq 1475 ∈ wcel 1977 ∃wrex 2897 ⊆ wss 3540 class class class wbr 4583 (class class class)co 6549 ℝcr 9814 0cc0 9815 · cmul 9820 < clt 9953 ≤ cle 9954 ℕcn 10897 2c2 10947 ℤcz 11254 ∥ cdvds 14821 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1713 ax-4 1728 ax-5 1827 ax-6 1875 ax-7 1922 ax-8 1979 ax-9 1986 ax-10 2006 ax-11 2021 ax-12 2034 ax-13 2234 ax-ext 2590 ax-sep 4709 ax-nul 4717 ax-pow 4769 ax-pr 4833 ax-un 6847 ax-resscn 9872 ax-1cn 9873 ax-icn 9874 ax-addcl 9875 ax-addrcl 9876 ax-mulcl 9877 ax-mulrcl 9878 ax-mulcom 9879 ax-addass 9880 ax-mulass 9881 ax-distr 9882 ax-i2m1 9883 ax-1ne0 9884 ax-1rid 9885 ax-rnegex 9886 ax-rrecex 9887 ax-cnre 9888 ax-pre-lttri 9889 ax-pre-lttrn 9890 ax-pre-ltadd 9891 ax-pre-mulgt0 9892 |
This theorem depends on definitions: df-bi 196 df-or 384 df-an 385 df-3or 1032 df-3an 1033 df-tru 1478 df-ex 1696 df-nf 1701 df-sb 1868 df-eu 2462 df-mo 2463 df-clab 2597 df-cleq 2603 df-clel 2606 df-nfc 2740 df-ne 2782 df-nel 2783 df-ral 2901 df-rex 2902 df-reu 2903 df-rmo 2904 df-rab 2905 df-v 3175 df-sbc 3403 df-csb 3500 df-dif 3543 df-un 3545 df-in 3547 df-ss 3554 df-pss 3556 df-nul 3875 df-if 4037 df-pw 4110 df-sn 4126 df-pr 4128 df-tp 4130 df-op 4132 df-uni 4373 df-iun 4457 df-br 4584 df-opab 4644 df-mpt 4645 df-tr 4681 df-eprel 4949 df-id 4953 df-po 4959 df-so 4960 df-fr 4997 df-we 4999 df-xp 5044 df-rel 5045 df-cnv 5046 df-co 5047 df-dm 5048 df-rn 5049 df-res 5050 df-ima 5051 df-pred 5597 df-ord 5643 df-on 5644 df-lim 5645 df-suc 5646 df-iota 5768 df-fun 5806 df-fn 5807 df-f 5808 df-f1 5809 df-fo 5810 df-f1o 5811 df-fv 5812 df-riota 6511 df-ov 6552 df-oprab 6553 df-mpt2 6554 df-om 6958 df-wrecs 7294 df-recs 7355 df-rdg 7393 df-er 7629 df-en 7842 df-dom 7843 df-sdom 7844 df-pnf 9955 df-mnf 9956 df-xr 9957 df-ltxr 9958 df-le 9959 df-sub 10147 df-neg 10148 df-div 10564 df-nn 10898 df-2 10956 df-n0 11170 df-z 11255 df-dvds 14822 |
This theorem is referenced by: lighneallem2 40061 |
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