Metamath Proof Explorer |
< Previous
Next >
Nearby theorems |
||
Mirrors > Home > MPE Home > Th. List > nnesq | Structured version Visualization version GIF version |
Description: A positive integer is even iff its square is even. (Contributed by NM, 20-Aug-2001.) (Revised by Mario Carneiro, 12-Sep-2015.) |
Ref | Expression |
---|---|
nnesq | ⊢ (𝑁 ∈ ℕ → ((𝑁 / 2) ∈ ℕ ↔ ((𝑁↑2) / 2) ∈ ℕ)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | nnz 12005 | . . . 4 ⊢ (𝑁 ∈ ℕ → 𝑁 ∈ ℤ) | |
2 | zesq 13588 | . . . 4 ⊢ (𝑁 ∈ ℤ → ((𝑁 / 2) ∈ ℤ ↔ ((𝑁↑2) / 2) ∈ ℤ)) | |
3 | 1, 2 | syl 17 | . . 3 ⊢ (𝑁 ∈ ℕ → ((𝑁 / 2) ∈ ℤ ↔ ((𝑁↑2) / 2) ∈ ℤ)) |
4 | nnrp 12401 | . . . . . 6 ⊢ (𝑁 ∈ ℕ → 𝑁 ∈ ℝ+) | |
5 | 4 | rphalfcld 12444 | . . . . 5 ⊢ (𝑁 ∈ ℕ → (𝑁 / 2) ∈ ℝ+) |
6 | 5 | rpgt0d 12435 | . . . 4 ⊢ (𝑁 ∈ ℕ → 0 < (𝑁 / 2)) |
7 | nnsqcl 13494 | . . . . . . 7 ⊢ (𝑁 ∈ ℕ → (𝑁↑2) ∈ ℕ) | |
8 | 7 | nnrpd 12430 | . . . . . 6 ⊢ (𝑁 ∈ ℕ → (𝑁↑2) ∈ ℝ+) |
9 | 8 | rphalfcld 12444 | . . . . 5 ⊢ (𝑁 ∈ ℕ → ((𝑁↑2) / 2) ∈ ℝ+) |
10 | 9 | rpgt0d 12435 | . . . 4 ⊢ (𝑁 ∈ ℕ → 0 < ((𝑁↑2) / 2)) |
11 | 6, 10 | 2thd 267 | . . 3 ⊢ (𝑁 ∈ ℕ → (0 < (𝑁 / 2) ↔ 0 < ((𝑁↑2) / 2))) |
12 | 3, 11 | anbi12d 632 | . 2 ⊢ (𝑁 ∈ ℕ → (((𝑁 / 2) ∈ ℤ ∧ 0 < (𝑁 / 2)) ↔ (((𝑁↑2) / 2) ∈ ℤ ∧ 0 < ((𝑁↑2) / 2)))) |
13 | elnnz 11992 | . 2 ⊢ ((𝑁 / 2) ∈ ℕ ↔ ((𝑁 / 2) ∈ ℤ ∧ 0 < (𝑁 / 2))) | |
14 | elnnz 11992 | . 2 ⊢ (((𝑁↑2) / 2) ∈ ℕ ↔ (((𝑁↑2) / 2) ∈ ℤ ∧ 0 < ((𝑁↑2) / 2))) | |
15 | 12, 13, 14 | 3bitr4g 316 | 1 ⊢ (𝑁 ∈ ℕ → ((𝑁 / 2) ∈ ℕ ↔ ((𝑁↑2) / 2) ∈ ℕ)) |
Colors of variables: wff setvar class |
Syntax hints: → wi 4 ↔ wb 208 ∧ wa 398 ∈ wcel 2114 class class class wbr 5066 (class class class)co 7156 0cc0 10537 < clt 10675 / cdiv 11297 ℕcn 11638 2c2 11693 ℤcz 11982 ↑cexp 13430 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1796 ax-4 1810 ax-5 1911 ax-6 1970 ax-7 2015 ax-8 2116 ax-9 2124 ax-10 2145 ax-11 2161 ax-12 2177 ax-ext 2793 ax-sep 5203 ax-nul 5210 ax-pow 5266 ax-pr 5330 ax-un 7461 ax-cnex 10593 ax-resscn 10594 ax-1cn 10595 ax-icn 10596 ax-addcl 10597 ax-addrcl 10598 ax-mulcl 10599 ax-mulrcl 10600 ax-mulcom 10601 ax-addass 10602 ax-mulass 10603 ax-distr 10604 ax-i2m1 10605 ax-1ne0 10606 ax-1rid 10607 ax-rnegex 10608 ax-rrecex 10609 ax-cnre 10610 ax-pre-lttri 10611 ax-pre-lttrn 10612 ax-pre-ltadd 10613 ax-pre-mulgt0 10614 |
This theorem depends on definitions: df-bi 209 df-an 399 df-or 844 df-3or 1084 df-3an 1085 df-tru 1540 df-ex 1781 df-nf 1785 df-sb 2070 df-mo 2622 df-eu 2654 df-clab 2800 df-cleq 2814 df-clel 2893 df-nfc 2963 df-ne 3017 df-nel 3124 df-ral 3143 df-rex 3144 df-reu 3145 df-rmo 3146 df-rab 3147 df-v 3496 df-sbc 3773 df-csb 3884 df-dif 3939 df-un 3941 df-in 3943 df-ss 3952 df-pss 3954 df-nul 4292 df-if 4468 df-pw 4541 df-sn 4568 df-pr 4570 df-tp 4572 df-op 4574 df-uni 4839 df-iun 4921 df-br 5067 df-opab 5129 df-mpt 5147 df-tr 5173 df-id 5460 df-eprel 5465 df-po 5474 df-so 5475 df-fr 5514 df-we 5516 df-xp 5561 df-rel 5562 df-cnv 5563 df-co 5564 df-dm 5565 df-rn 5566 df-res 5567 df-ima 5568 df-pred 6148 df-ord 6194 df-on 6195 df-lim 6196 df-suc 6197 df-iota 6314 df-fun 6357 df-fn 6358 df-f 6359 df-f1 6360 df-fo 6361 df-f1o 6362 df-fv 6363 df-riota 7114 df-ov 7159 df-oprab 7160 df-mpo 7161 df-om 7581 df-2nd 7690 df-wrecs 7947 df-recs 8008 df-rdg 8046 df-er 8289 df-en 8510 df-dom 8511 df-sdom 8512 df-pnf 10677 df-mnf 10678 df-xr 10679 df-ltxr 10680 df-le 10681 df-sub 10872 df-neg 10873 df-div 11298 df-nn 11639 df-2 11701 df-n0 11899 df-z 11983 df-uz 12245 df-rp 12391 df-seq 13371 df-exp 13431 |
This theorem is referenced by: sqrt2irrlem 15601 |
Copyright terms: Public domain | W3C validator |