MPE Home Metamath Proof Explorer < Previous   Next >
Nearby theorems
Mirrors  >  Home  >  MPE Home  >  Th. List  >  recmulnq Structured version   Visualization version   GIF version

Theorem recmulnq 11076
Description: Relationship between reciprocal and multiplication on positive fractions. (Contributed by NM, 6-Mar-1996.) (Revised by Mario Carneiro, 28-Apr-2015.) (New usage is discouraged.)
Assertion
Ref Expression
recmulnq (𝐴 ∈ Q → ((*Q‘𝐴) = 𝐵 ↔ (𝐴 ·Q 𝐵) = 1Q))

Proof of Theorem recmulnq
Dummy variables 𝑥 𝑦 𝑠 𝑟 𝑡 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 fvex 6921 . . . 4 (*Q‘𝐴) ∈ V
21a1i 11 . . 3 (𝐴 ∈ Q → (*Q‘𝐴) ∈ V)
3 eleq1 2852 . . 3 ((*Q‘𝐴) = 𝐵 → ((*Q‘𝐴) ∈ V ↔ 𝐵 ∈ V))
42, 3syl5ibcom 248 . 2 (𝐴 ∈ Q → ((*Q‘𝐴) = 𝐵 → 𝐵 ∈ V))
5 id 23 . . . . . 6 ((𝐴 ·Q 𝐵) = 1Q → (𝐴 ·Q 𝐵) = 1Q)
6 1nq 11040 . . . . . 6 1Q ∈ Q
75, 6eqeltrdi 2872 . . . . 5 ((𝐴 ·Q 𝐵) = 1Q → (𝐴 ·Q 𝐵) ∈ Q)
8 mulnqf 11061 . . . . . . 7 ·Q :(Q × Q)⟶Q
98fdmi 6743 . . . . . 6 dom ·Q = (Q × Q)
10 0nnq 11036 . . . . . 6 ¬ ∅ ∈ Q
119, 10ndmovrcl 7631 . . . . 5 ((𝐴 ·Q 𝐵) ∈ Q → (𝐴 ∈ Q ∧ 𝐵 ∈ Q))
127, 11syl 18 . . . 4 ((𝐴 ·Q 𝐵) = 1Q → (𝐴 ∈ Q ∧ 𝐵 ∈ Q))
13 elex 3475 . . . 4 (𝐵 ∈ Q → 𝐵 ∈ V)
1412, 13simpl2im 513 . . 3 ((𝐴 ·Q 𝐵) = 1Q → 𝐵 ∈ V)
1514a1i 11 . 2 (𝐴 ∈ Q → ((𝐴 ·Q 𝐵) = 1Q → 𝐵 ∈ V))
16 oveq1 7450 . . . . 5 (𝑥 = 𝐴 → (𝑥 ·Q 𝑦) = (𝐴 ·Q 𝑦))
1716eqeq1d 2765 . . . 4 (𝑥 = 𝐴 → ((𝑥 ·Q 𝑦) = 1Q ↔ (𝐴 ·Q 𝑦) = 1Q))
18 oveq2 7451 . . . . 5 (𝑦 = 𝐵 → (𝐴 ·Q 𝑦) = (𝐴 ·Q 𝐵))
1918eqeq1d 2765 . . . 4 (𝑦 = 𝐵 → ((𝐴 ·Q 𝑦) = 1Q ↔ (𝐴 ·Q 𝐵) = 1Q))
20 nqerid 11045 . . . . . . . . . 10 (𝑥 ∈ Q → ([Q]‘𝑥) = 𝑥)
21 relxp 5673 . . . . . . . . . . . 12 Rel (N × N)
22 elpqn 11037 . . . . . . . . . . . 12 (𝑥 ∈ Q → 𝑥 ∈ (N × N))
23 1st2nd 8074 . . . . . . . . . . . 12 ((Rel (N × N) ∧ 𝑥 ∈ (N × N)) → 𝑥 = ⟨(1st ‘𝑥), (2nd ‘𝑥)⟩)
2421, 22, 23sylancr 599 . . . . . . . . . . 11 (𝑥 ∈ Q → 𝑥 = ⟨(1st ‘𝑥), (2nd ‘𝑥)⟩)
2524fveq2d 6912 . . . . . . . . . 10 (𝑥 ∈ Q → ([Q]‘𝑥) = ([Q]‘⟨(1st ‘𝑥), (2nd ‘𝑥)⟩))
2620, 25eqtr3d 2800 . . . . . . . . 9 (𝑥 ∈ Q → 𝑥 = ([Q]‘⟨(1st ‘𝑥), (2nd ‘𝑥)⟩))
2726oveq1d 7458 . . . . . . . 8 (𝑥 ∈ Q → (𝑥 ·Q ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)) = (([Q]‘⟨(1st ‘𝑥), (2nd ‘𝑥)⟩) ·Q ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)))
28 mulerpq 11069 . . . . . . . 8 (([Q]‘⟨(1st ‘𝑥), (2nd ‘𝑥)⟩) ·Q ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)) = ([Q]‘(⟨(1st ‘𝑥), (2nd ‘𝑥)⟩ ·pQ ⟨(2nd ‘𝑥), (1st ‘𝑥)⟩))
2927, 28eqtrdi 2814 . . . . . . 7 (𝑥 ∈ Q → (𝑥 ·Q ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)) = ([Q]‘(⟨(1st ‘𝑥), (2nd ‘𝑥)⟩ ·pQ ⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)))
30 xp1st 8057 . . . . . . . . . . 11 (𝑥 ∈ (N × N) → (1st ‘𝑥) ∈ N)
3122, 30syl 18 . . . . . . . . . 10 (𝑥 ∈ Q → (1st ‘𝑥) ∈ N)
32 xp2nd 8058 . . . . . . . . . . 11 (𝑥 ∈ (N × N) → (2nd ‘𝑥) ∈ N)
3322, 32syl 18 . . . . . . . . . 10 (𝑥 ∈ Q → (2nd ‘𝑥) ∈ N)
34 mulpipq 11052 . . . . . . . . . 10 ((((1st ‘𝑥) ∈ N ∧ (2nd ‘𝑥) ∈ N) ∧ ((2nd ‘𝑥) ∈ N ∧ (1st ‘𝑥) ∈ N)) → (⟨(1st ‘𝑥), (2nd ‘𝑥)⟩ ·pQ ⟨(2nd ‘𝑥), (1st ‘𝑥)⟩) = ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((2nd ‘𝑥) ·N (1st ‘𝑥))⟩)
3531, 33, 33, 31, 34syl22anc 852 . . . . . . . . 9 (𝑥 ∈ Q → (⟨(1st ‘𝑥), (2nd ‘𝑥)⟩ ·pQ ⟨(2nd ‘𝑥), (1st ‘𝑥)⟩) = ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((2nd ‘𝑥) ·N (1st ‘𝑥))⟩)
36 mulcompi 11008 . . . . . . . . . 10 ((2nd ‘𝑥) ·N (1st ‘𝑥)) = ((1st ‘𝑥) ·N (2nd ‘𝑥))
3736opeq2i 4847 . . . . . . . . 9 ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((2nd ‘𝑥) ·N (1st ‘𝑥))⟩ = ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩
3835, 37eqtrdi 2814 . . . . . . . 8 (𝑥 ∈ Q → (⟨(1st ‘𝑥), (2nd ‘𝑥)⟩ ·pQ ⟨(2nd ‘𝑥), (1st ‘𝑥)⟩) = ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩)
3938fveq2d 6912 . . . . . . 7 (𝑥 ∈ Q → ([Q]‘(⟨(1st ‘𝑥), (2nd ‘𝑥)⟩ ·pQ ⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)) = ([Q]‘⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩))
40 mulclpi 11005 . . . . . . . . . . 11 (((1st ‘𝑥) ∈ N ∧ (2nd ‘𝑥) ∈ N) → ((1st ‘𝑥) ·N (2nd ‘𝑥)) ∈ N)
4131, 33, 40syl2anc 596 . . . . . . . . . 10 (𝑥 ∈ Q → ((1st ‘𝑥) ·N (2nd ‘𝑥)) ∈ N)
42 1nqenq 11074 . . . . . . . . . 10 (((1st ‘𝑥) ·N (2nd ‘𝑥)) ∈ N → 1Q ~Q ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩)
4341, 42syl 18 . . . . . . . . 9 (𝑥 ∈ Q → 1Q ~Q ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩)
44 elpqn 11037 . . . . . . . . . . 11 (1Q ∈ Q → 1Q ∈ (N × N))
456, 44ax-mp 5 . . . . . . . . . 10 1Q ∈ (N × N)
4641, 41opelxpd 5694 . . . . . . . . . 10 (𝑥 ∈ Q → ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩ ∈ (N × N))
47 nqereq 11047 . . . . . . . . . 10 ((1Q ∈ (N × N) ∧ ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩ ∈ (N × N)) → (1Q ~Q ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩ ↔ ([Q]‘1Q) = ([Q]‘⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩)))
4845, 46, 47sylancr 599 . . . . . . . . 9 (𝑥 ∈ Q → (1Q ~Q ⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩ ↔ ([Q]‘1Q) = ([Q]‘⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩)))
4943, 48mpbid 235 . . . . . . . 8 (𝑥 ∈ Q → ([Q]‘1Q) = ([Q]‘⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩))
50 nqerid 11045 . . . . . . . . 9 (1Q ∈ Q → ([Q]‘1Q) = 1Q)
516, 50ax-mp 5 . . . . . . . 8 ([Q]‘1Q) = 1Q
5249, 51eqtr3di 2813 . . . . . . 7 (𝑥 ∈ Q → ([Q]‘⟨((1st ‘𝑥) ·N (2nd ‘𝑥)), ((1st ‘𝑥) ·N (2nd ‘𝑥))⟩) = 1Q)
5329, 39, 523eqtrd 2802 . . . . . 6 (𝑥 ∈ Q → (𝑥 ·Q ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)) = 1Q)
54 fvex 6921 . . . . . . 7 ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩) ∈ V
55 oveq2 7451 . . . . . . . 8 (𝑦 = ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩) → (𝑥 ·Q 𝑦) = (𝑥 ·Q ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)))
5655eqeq1d 2765 . . . . . . 7 (𝑦 = ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩) → ((𝑥 ·Q 𝑦) = 1Q ↔ (𝑥 ·Q ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)) = 1Q))
5754, 56spcev 3564 . . . . . 6 ((𝑥 ·Q ([Q]‘⟨(2nd ‘𝑥), (1st ‘𝑥)⟩)) = 1Q → ∃𝑦(𝑥 ·Q 𝑦) = 1Q)
5853, 57syl 18 . . . . 5 (𝑥 ∈ Q → ∃𝑦(𝑥 ·Q 𝑦) = 1Q)
59 mulcomnq 11065 . . . . . 6 (𝑟 ·Q 𝑠) = (𝑠 ·Q 𝑟)
60 mulassnq 11071 . . . . . 6 ((𝑟 ·Q 𝑠) ·Q 𝑡) = (𝑟 ·Q (𝑠 ·Q 𝑡))
61 mulidnq 11075 . . . . . 6 (𝑟 ∈ Q → (𝑟 ·Q 1Q) = 𝑟)
626, 9, 10, 59, 60, 61caovmo 7682 . . . . 5 ∃*𝑦(𝑥 ·Q 𝑦) = 1Q
63 df-eu 2597 . . . . 5 (∃!𝑦(𝑥 ·Q 𝑦) = 1Q ↔ (∃𝑦(𝑥 ·Q 𝑦) = 1Q ∧ ∃*𝑦(𝑥 ·Q 𝑦) = 1Q))
6458, 62, 63sylanblrc 602 . . . 4 (𝑥 ∈ Q → ∃!𝑦(𝑥 ·Q 𝑦) = 1Q)
65 cnvimass 6211 . . . . . . . 8 (◡ ·Q “ {1Q}) ⊆ dom ·Q
66 df-rq 11029 . . . . . . . 8 *Q = (◡ ·Q “ {1Q})
679eqcomi 2772 . . . . . . . 8 (Q × Q) = dom ·Q
6865, 66, 673sstr4i 3964 . . . . . . 7 *Q ⊆ (Q × Q)
69 relxp 5673 . . . . . . 7 Rel (Q × Q)
70 relss 5763 . . . . . . 7 (*Q ⊆ (Q × Q) → (Rel (Q × Q) → Rel *Q))
7168, 69, 70mp2 9 . . . . . 6 Rel *Q
7266eleq2i 2856 . . . . . . . 8 (⟨𝑥, 𝑦⟩ ∈ *Q ↔ ⟨𝑥, 𝑦⟩ ∈ (◡ ·Q “ {1Q}))
73 ffn 6731 . . . . . . . . 9 ( ·Q :(Q × Q)⟶Q → ·Q Fn (Q × Q))
74 fniniseg 7083 . . . . . . . . 9 ( ·Q Fn (Q × Q) → (⟨𝑥, 𝑦⟩ ∈ (◡ ·Q “ {1Q}) ↔ (⟨𝑥, 𝑦⟩ ∈ (Q × Q) ∧ ( ·Q ‘⟨𝑥, 𝑦⟩) = 1Q)))
758, 73, 74mp2b 10 . . . . . . . 8 (⟨𝑥, 𝑦⟩ ∈ (◡ ·Q “ {1Q}) ↔ (⟨𝑥, 𝑦⟩ ∈ (Q × Q) ∧ ( ·Q ‘⟨𝑥, 𝑦⟩) = 1Q))
76 ancom 466 . . . . . . . . 9 ((⟨𝑥, 𝑦⟩ ∈ (Q × Q) ∧ ( ·Q ‘⟨𝑥, 𝑦⟩) = 1Q) ↔ (( ·Q ‘⟨𝑥, 𝑦⟩) = 1Q ∧ ⟨𝑥, 𝑦⟩ ∈ (Q × Q)))
77 ancom 466 . . . . . . . . . 10 ((𝑥 ∈ Q ∧ (𝑥 ·Q 𝑦) = 1Q) ↔ ((𝑥 ·Q 𝑦) = 1Q ∧ 𝑥 ∈ Q))
78 eleq1 2852 . . . . . . . . . . . . . . 15 ((𝑥 ·Q 𝑦) = 1Q → ((𝑥 ·Q 𝑦) ∈ Q ↔ 1Q ∈ Q))
796, 78mpbiri 261 . . . . . . . . . . . . . 14 ((𝑥 ·Q 𝑦) = 1Q → (𝑥 ·Q 𝑦) ∈ Q)
809, 10ndmovrcl 7631 . . . . . . . . . . . . . 14 ((𝑥 ·Q 𝑦) ∈ Q → (𝑥 ∈ Q ∧ 𝑦 ∈ Q))
8179, 80syl 18 . . . . . . . . . . . . 13 ((𝑥 ·Q 𝑦) = 1Q → (𝑥 ∈ Q ∧ 𝑦 ∈ Q))
82 opelxpi 5692 . . . . . . . . . . . . 13 ((𝑥 ∈ Q ∧ 𝑦 ∈ Q) → ⟨𝑥, 𝑦⟩ ∈ (Q × Q))
8381, 82syl 18 . . . . . . . . . . . 12 ((𝑥 ·Q 𝑦) = 1Q → ⟨𝑥, 𝑦⟩ ∈ (Q × Q))
8481simpld 500 . . . . . . . . . . . 12 ((𝑥 ·Q 𝑦) = 1Q → 𝑥 ∈ Q)
8583, 842thd 268 . . . . . . . . . . 11 ((𝑥 ·Q 𝑦) = 1Q → (⟨𝑥, 𝑦⟩ ∈ (Q × Q) ↔ 𝑥 ∈ Q))
8685pm5.32i 585 . . . . . . . . . 10 (((𝑥 ·Q 𝑦) = 1Q ∧ ⟨𝑥, 𝑦⟩ ∈ (Q × Q)) ↔ ((𝑥 ·Q 𝑦) = 1Q ∧ 𝑥 ∈ Q))
87 df-ov 7446 . . . . . . . . . . . 12 (𝑥 ·Q 𝑦) = ( ·Q ‘⟨𝑥, 𝑦⟩)
8887eqeq1i 2768 . . . . . . . . . . 11 ((𝑥 ·Q 𝑦) = 1Q ↔ ( ·Q ‘⟨𝑥, 𝑦⟩) = 1Q)
8988anbi1i 636 . . . . . . . . . 10 (((𝑥 ·Q 𝑦) = 1Q ∧ ⟨𝑥, 𝑦⟩ ∈ (Q × Q)) ↔ (( ·Q ‘⟨𝑥, 𝑦⟩) = 1Q ∧ ⟨𝑥, 𝑦⟩ ∈ (Q × Q)))
9077, 86, 893bitr2ri 303 . . . . . . . . 9 ((( ·Q ‘⟨𝑥, 𝑦⟩) = 1Q ∧ ⟨𝑥, 𝑦⟩ ∈ (Q × Q)) ↔ (𝑥 ∈ Q ∧ (𝑥 ·Q 𝑦) = 1Q))
9176, 90bitri 278 . . . . . . . 8 ((⟨𝑥, 𝑦⟩ ∈ (Q × Q) ∧ ( ·Q ‘⟨𝑥, 𝑦⟩) = 1Q) ↔ (𝑥 ∈ Q ∧ (𝑥 ·Q 𝑦) = 1Q))
9272, 75, 913bitri 300 . . . . . . 7 (⟨𝑥, 𝑦⟩ ∈ *Q ↔ (𝑥 ∈ Q ∧ (𝑥 ·Q 𝑦) = 1Q))
9392a1i 11 . . . . . 6 (⊤ → (⟨𝑥, 𝑦⟩ ∈ *Q ↔ (𝑥 ∈ Q ∧ (𝑥 ·Q 𝑦) = 1Q)))
9471, 93opabbi2dv 5833 . . . . 5 (⊤ → *Q = {⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ Q ∧ (𝑥 ·Q 𝑦) = 1Q)})
9594mptru 1577 . . . 4 *Q = {⟨𝑥, 𝑦⟩ ∣ (𝑥 ∈ Q ∧ (𝑥 ·Q 𝑦) = 1Q)}
9617, 19, 64, 95fvopab3g 7011 . . 3 ((𝐴 ∈ Q ∧ 𝐵 ∈ V) → ((*Q‘𝐴) = 𝐵 ↔ (𝐴 ·Q 𝐵) = 1Q))
9796ex 418 . 2 (𝐴 ∈ Q → (𝐵 ∈ V → ((*Q‘𝐴) = 𝐵 ↔ (𝐴 ·Q 𝐵) = 1Q)))
984, 15, 97pm5.21ndd 382 1 (𝐴 ∈ Q → ((*Q‘𝐴) = 𝐵 ↔ (𝐴 ·Q 𝐵) = 1Q))
Colors of variables:    wff setvar class
This proof depends on syntax axioms:   → wi 4   ↔ wb 209   ∧ wa 401   = wceq 1570  ⊤wtru 1571  ∃wex 1812   ∈ wcel 2147  ∃*wmo 2565  ∃!weu 2596  Vcvv 3454   ⊆ wss 3900  {csn 4588  ⟨cop 4838   class class class wbr 5106  {copab 5170   × cxp 5653  ◡ccnv 5654  dom cdm 5655   “ cima 5658  Rel wrel 5660   Fn wfn 6553  ⟶wf 6554  ‘cfv 6558  (class class class)co 7443  1st c1st 8023  2nd c2nd 8024  Ncnpi 10956   ·N cmi 10958   ·pQ cmpq 10961   ~Q ceq 10963  Qcnq 10964  1Qc1q 10965  [Q]cerq 10966   ·Q cmq 10968  *Qcrq 10969
This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1945  ax-6 2002  ax-7 2043  ax-8 2149  ax-9 2157  ax-10 2180  ax-11 2197  ax-12 2216  ax-ext 2735  ax-sep 5252  ax-nul 5263  ax-pr 5395  ax-un 7775
This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3or 1104  df-3an 1105  df-tru 1573  df-fal 1583  df-ex 1813  df-nf 1817  df-sb 2102  df-mo 2567  df-eu 2597  df-clab 2742  df-cleq 2755  df-clel 2839  df-nfc 2913  df-ne 2960  df-ral 3081  df-rex 3091  df-rmo 3369  df-reu 3370  df-rab 3417  df-v 3456  df-sbc 3743  df-csb 3852  df-ss 3901  df-pss 4017  df-dif 4050  df-in 4094  df-un 4154  df-nul 4282  df-if 4486  df-pw 4562  df-sn 4589  df-pr 4591  df-op 4839  df-uni 4871  df-iun 4956  df-br 5107  df-opab 5171  df-mpt 5190  df-tr 5216  df-id 5550  df-eprel 5555  df-po 5563  df-so 5564  df-fr 5608  df-we 5610  df-xp 5661  df-rel 5662  df-cnv 5663  df-co 5664  df-dm 5665  df-rn 5666  df-res 5667  df-ima 5668  df-pred 6322  df-ord 6383  df-on 6384  df-lim 6385  df-suc 6386  df-iota 6512  df-fun 6560  df-fn 6561  df-f 6562  df-f1 6563  df-fo 6564  df-f1o 6565  df-fv 6566  df-ov 7446  df-oprab 7447  df-mpo 7448  df-om 7902  df-1st 8025  df-2nd 8026  df-frecs 8327  df-wrecs 8358  df-recs 8407  df-rdg 8446  df-1o 8504  df-oadd 8508  df-omul 8509  df-er 8745  df-ni 10984  df-mi 10986  df-lti 10987  df-mpq 11021  df-enq 11023  df-nq 11024  df-erq 11025  df-mq 11027  df-1nq 11028  df-rq 11029
This theorem is used by:  recidnq  11077  recrecnq  11079  reclem3pr  11161
  Copyright terms: Public domain W3C validator