Metamath Proof Explorer


Theorem evl1deg2

Description: Evaluation of a univariate polynomial of degree 2. (Contributed by Thierry Arnoux, 22-Jun-2025)

Ref Expression
Hypotheses evl1deg1.1 ⊢ P = Poly 1 ⁡ R
evl1deg1.2 ⊢ O = eval 1 ⁡ R
evl1deg1.3 ⊢ K = Base R
evl1deg1.4 ⊢ U = Base P
evl1deg1.5 ⊢ · ˙ = ⋅ R
evl1deg1.6 ⊢ + ˙ = + R
evl1deg2.p ⊢ × ˙ = ⋅ mulGrp R
evl1deg2.f ⊢ F = coe 1 ⁡ M
evl1deg2.e ⊢ E = deg 1 ⁡ R
evl1deg2.a ⊢ A = F ⁡ 2
evl1deg2.b ⊢ B = F ⁡ 1
evl1deg2.c ⊢ C = F ⁡ 0
evl1deg2.r ⊢ φ → R ∈ CRing
evl1deg2.m ⊢ φ → M ∈ U
evl1deg2.1 ⊢ φ → E ⁡ M = 2
evl1deg2.x ⊢ φ → X ∈ K
Assertion evl1deg2 ⊢ φ → O ⁡ M ⁡ X = A · ˙ 2 × ˙ X + ˙ B · ˙ X + ˙ C

Proof

Step Hyp Ref Expression
1 evl1deg1.1 ⊢ P = Poly 1 ⁡ R
2 evl1deg1.2 ⊢ O = eval 1 ⁡ R
3 evl1deg1.3 ⊢ K = Base R
4 evl1deg1.4 ⊢ U = Base P
5 evl1deg1.5 ⊢ · ˙ = ⋅ R
6 evl1deg1.6 ⊢ + ˙ = + R
7 evl1deg2.p ⊢ × ˙ = ⋅ mulGrp R
8 evl1deg2.f ⊢ F = coe 1 ⁡ M
9 evl1deg2.e ⊢ E = deg 1 ⁡ R
10 evl1deg2.a ⊢ A = F ⁡ 2
11 evl1deg2.b ⊢ B = F ⁡ 1
12 evl1deg2.c ⊢ C = F ⁡ 0
13 evl1deg2.r ⊢ φ → R ∈ CRing
14 evl1deg2.m ⊢ φ → M ∈ U
15 evl1deg2.1 ⊢ φ → E ⁡ M = 2
16 evl1deg2.x ⊢ φ → X ∈ K
17 oveq2 ⊢ x = X → k × ˙ x = k × ˙ X
18 17 oveq2d ⊢ x = X → F ⁡ k · ˙ k × ˙ x = F ⁡ k · ˙ k × ˙ X
19 18 mpteq2dv ⊢ x = X → k ∈ ℕ 0 ⟼ F ⁡ k · ˙ k × ˙ x = k ∈ ℕ 0 ⟼ F ⁡ k · ˙ k × ˙ X
20 19 oveq2d ⊢ x = X → ∑ R k ∈ ℕ 0 F ⁡ k · ˙ k × ˙ x = ∑ R k ∈ ℕ 0 F ⁡ k · ˙ k × ˙ X
21 2 1 3 4 13 14 5 7 8 evl1fpws ⊢ φ → O ⁡ M = x ∈ K ⟼ ∑ R k ∈ ℕ 0 F ⁡ k · ˙ k × ˙ x
22 ovexd ⊢ φ → ∑ R k ∈ ℕ 0 F ⁡ k · ˙ k × ˙ X ∈ V
23 20 21 16 22 fvmptd4 ⊢ φ → O ⁡ M ⁡ X = ∑ R k ∈ ℕ 0 F ⁡ k · ˙ k × ˙ X
24 eqid ⊢ 0 R = 0 R
25 13 crngringd ⊢ φ → R ∈ Ring
26 25 ringcmnd ⊢ φ → R ∈ CMnd
27 nn0ex ⊢ ℕ 0 ∈ V
28 27 a1i ⊢ φ → ℕ 0 ∈ V
29 25 adantr ⊢ φ ∧ k ∈ ℕ 0 → R ∈ Ring
30 8 4 1 3 coe1fvalcl ⊢ M ∈ U ∧ k ∈ ℕ 0 → F ⁡ k ∈ K
31 14 30 sylan ⊢ φ ∧ k ∈ ℕ 0 → F ⁡ k ∈ K
32 eqid ⊢ mulGrp R = mulGrp R
33 32 3 mgpbas ⊢ K = Base mulGrp R
34 32 ringmgp ⊢ R ∈ Ring → mulGrp R ∈ Mnd
35 25 34 syl ⊢ φ → mulGrp R ∈ Mnd
36 35 adantr ⊢ φ ∧ k ∈ ℕ 0 → mulGrp R ∈ Mnd
37 simpr ⊢ φ ∧ k ∈ ℕ 0 → k ∈ ℕ 0
38 16 adantr ⊢ φ ∧ k ∈ ℕ 0 → X ∈ K
39 33 7 36 37 38 mulgnn0cld ⊢ φ ∧ k ∈ ℕ 0 → k × ˙ X ∈ K
40 3 5 29 31 39 ringcld ⊢ φ ∧ k ∈ ℕ 0 → F ⁡ k · ˙ k × ˙ X ∈ K
41 fvexd ⊢ φ → 0 R ∈ V
42 fveq2 ⊢ k = j → F ⁡ k = F ⁡ j
43 oveq1 ⊢ k = j → k × ˙ X = j × ˙ X
44 42 43 oveq12d ⊢ k = j → F ⁡ k · ˙ k × ˙ X = F ⁡ j · ˙ j × ˙ X
45 breq1 ⊢ i = E ⁡ M → i < j ↔ E ⁡ M < j
46 45 imbi1d ⊢ i = E ⁡ M → i < j → F ⁡ j · ˙ j × ˙ X = 0 R ↔ E ⁡ M < j → F ⁡ j · ˙ j × ˙ X = 0 R
47 46 ralbidv ⊢ i = E ⁡ M → ∀ j ∈ ℕ 0 i < j → F ⁡ j · ˙ j × ˙ X = 0 R ↔ ∀ j ∈ ℕ 0 E ⁡ M < j → F ⁡ j · ˙ j × ˙ X = 0 R
48 2nn0 ⊢ 2 ∈ ℕ 0
49 48 a1i ⊢ φ → 2 ∈ ℕ 0
50 15 49 eqeltrd ⊢ φ → E ⁡ M ∈ ℕ 0
51 14 ad2antrr ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → M ∈ U
52 simplr ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → j ∈ ℕ 0
53 simpr ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → E ⁡ M < j
54 9 1 4 24 8 deg1lt ⊢ M ∈ U ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → F ⁡ j = 0 R
55 51 52 53 54 syl3anc ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → F ⁡ j = 0 R
56 55 oveq1d ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → F ⁡ j · ˙ j × ˙ X = 0 R · ˙ j × ˙ X
57 25 ad2antrr ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → R ∈ Ring
58 57 34 syl ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → mulGrp R ∈ Mnd
59 16 ad2antrr ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → X ∈ K
60 33 7 58 52 59 mulgnn0cld ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → j × ˙ X ∈ K
61 3 5 24 57 60 ringlzd ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → 0 R · ˙ j × ˙ X = 0 R
62 56 61 eqtrd ⊢ φ ∧ j ∈ ℕ 0 ∧ E ⁡ M < j → F ⁡ j · ˙ j × ˙ X = 0 R
63 62 ex ⊢ φ ∧ j ∈ ℕ 0 → E ⁡ M < j → F ⁡ j · ˙ j × ˙ X = 0 R
64 63 ralrimiva ⊢ φ → ∀ j ∈ ℕ 0 E ⁡ M < j → F ⁡ j · ˙ j × ˙ X = 0 R
65 47 50 64 rspcedvdw ⊢ φ → ∃ i ∈ ℕ 0 ∀ j ∈ ℕ 0 i < j → F ⁡ j · ˙ j × ˙ X = 0 R
66 41 40 44 65 mptnn0fsuppd ⊢ φ → finSupp 0 R⁡ k ∈ ℕ 0 ⟼ F ⁡ k · ˙ k × ˙ X
67 fzouzdisj ⊢ 0 ..^ 3 ∩ ℤ ≥ 3 = ∅
68 67 a1i ⊢ φ → 0 ..^ 3 ∩ ℤ ≥ 3 = ∅
69 nn0uz ⊢ ℕ 0 = ℤ ≥ 0
70 3nn0 ⊢ 3 ∈ ℕ 0
71 70 69 eleqtri ⊢ 3 ∈ ℤ ≥ 0
72 fzouzsplit ⊢ 3 ∈ ℤ ≥ 0 → ℤ ≥ 0 = 0 ..^ 3 ∪ ℤ ≥ 3
73 71 72 ax-mp ⊢ ℤ ≥ 0 = 0 ..^ 3 ∪ ℤ ≥ 3
74 69 73 eqtri ⊢ ℕ 0 = 0 ..^ 3 ∪ ℤ ≥ 3
75 74 a1i ⊢ φ → ℕ 0 = 0 ..^ 3 ∪ ℤ ≥ 3
76 3 24 6 26 28 40 66 68 75 gsumsplit2 ⊢ φ → ∑ R k ∈ ℕ 0 F ⁡ k · ˙ k × ˙ X = ∑ R k ∈ 0 ..^ 3 F ⁡ k · ˙ k × ˙ X + ˙ ∑ R k ∈ ℤ ≥ 3 F ⁡ k · ˙ k × ˙ X
77 fzo0to3tp ⊢ 0 ..^ 3 = 0 1 2
78 77 a1i ⊢ φ → 0 ..^ 3 = 0 1 2
79 78 mpteq1d ⊢ φ → k ∈ 0 ..^ 3 ⟼ F ⁡ k · ˙ k × ˙ X = k ∈ 0 1 2 ⟼ F ⁡ k · ˙ k × ˙ X
80 79 oveq2d ⊢ φ → ∑ R k ∈ 0 ..^ 3 F ⁡ k · ˙ k × ˙ X = ∑ R k ∈ 0 1 2 F ⁡ k · ˙ k × ˙ X
81 14 adantr ⊢ φ ∧ k ∈ ℤ ≥ 3 → M ∈ U
82 uzss ⊢ 3 ∈ ℤ ≥ 0 → ℤ ≥ 3 ⊆ ℤ ≥ 0
83 71 82 ax-mp ⊢ ℤ ≥ 3 ⊆ ℤ ≥ 0
84 83 69 sseqtrri ⊢ ℤ ≥ 3 ⊆ ℕ 0
85 84 a1i ⊢ φ → ℤ ≥ 3 ⊆ ℕ 0
86 85 sselda ⊢ φ ∧ k ∈ ℤ ≥ 3 → k ∈ ℕ 0
87 15 adantr ⊢ φ ∧ k ∈ ℤ ≥ 3 → E ⁡ M = 2
88 2p1e3 ⊢ 2 + 1 = 3
89 88 fveq2i ⊢ ℤ ≥ 2 + 1 = ℤ ≥ 3
90 89 eleq2i ⊢ k ∈ ℤ ≥ 2 + 1 ↔ k ∈ ℤ ≥ 3
91 2z ⊢ 2 ∈ ℤ
92 eluzp1l ⊢ 2 ∈ ℤ ∧ k ∈ ℤ ≥ 2 + 1 → 2 < k
93 91 92 mpan ⊢ k ∈ ℤ ≥ 2 + 1 → 2 < k
94 90 93 sylbir ⊢ k ∈ ℤ ≥ 3 → 2 < k
95 94 adantl ⊢ φ ∧ k ∈ ℤ ≥ 3 → 2 < k
96 87 95 eqbrtrd ⊢ φ ∧ k ∈ ℤ ≥ 3 → E ⁡ M < k
97 9 1 4 24 8 deg1lt ⊢ M ∈ U ∧ k ∈ ℕ 0 ∧ E ⁡ M < k → F ⁡ k = 0 R
98 81 86 96 97 syl3anc ⊢ φ ∧ k ∈ ℤ ≥ 3 → F ⁡ k = 0 R
99 98 oveq1d ⊢ φ ∧ k ∈ ℤ ≥ 3 → F ⁡ k · ˙ k × ˙ X = 0 R · ˙ k × ˙ X
100 25 adantr ⊢ φ ∧ k ∈ ℤ ≥ 3 → R ∈ Ring
101 100 34 syl ⊢ φ ∧ k ∈ ℤ ≥ 3 → mulGrp R ∈ Mnd
102 16 adantr ⊢ φ ∧ k ∈ ℤ ≥ 3 → X ∈ K
103 33 7 101 86 102 mulgnn0cld ⊢ φ ∧ k ∈ ℤ ≥ 3 → k × ˙ X ∈ K
104 3 5 24 100 103 ringlzd ⊢ φ ∧ k ∈ ℤ ≥ 3 → 0 R · ˙ k × ˙ X = 0 R
105 99 104 eqtrd ⊢ φ ∧ k ∈ ℤ ≥ 3 → F ⁡ k · ˙ k × ˙ X = 0 R
106 105 mpteq2dva ⊢ φ → k ∈ ℤ ≥ 3 ⟼ F ⁡ k · ˙ k × ˙ X = k ∈ ℤ ≥ 3 ⟼ 0 R
107 106 oveq2d ⊢ φ → ∑ R k ∈ ℤ ≥ 3 F ⁡ k · ˙ k × ˙ X = ∑ R k ∈ ℤ ≥ 3 0 R
108 13 crnggrpd ⊢ φ → R ∈ Grp
109 108 grpmndd ⊢ φ → R ∈ Mnd
110 fvexd ⊢ φ → ℤ ≥ 3 ∈ V
111 24 gsumz ⊢ R ∈ Mnd ∧ ℤ ≥ 3 ∈ V → ∑ R k ∈ ℤ ≥ 3 0 R = 0 R
112 109 110 111 syl2anc ⊢ φ → ∑ R k ∈ ℤ ≥ 3 0 R = 0 R
113 107 112 eqtrd ⊢ φ → ∑ R k ∈ ℤ ≥ 3 F ⁡ k · ˙ k × ˙ X = 0 R
114 80 113 oveq12d ⊢ φ → ∑ R k ∈ 0 ..^ 3 F ⁡ k · ˙ k × ˙ X + ˙ ∑ R k ∈ ℤ ≥ 3 F ⁡ k · ˙ k × ˙ X = ∑ R k ∈ 0 1 2 F ⁡ k · ˙ k × ˙ X + ˙ 0 R
115 tpex ⊢ 0 1 2 ∈ V
116 115 a1i ⊢ φ → 0 1 2 ∈ V
117 25 adantr ⊢ φ ∧ k ∈ 0 1 2 → R ∈ Ring
118 8 4 1 3 coe1f ⊢ M ∈ U → F : ℕ 0 ⟶ K
119 14 118 syl ⊢ φ → F : ℕ 0 ⟶ K
120 119 adantr ⊢ φ ∧ k ∈ 0 1 2 → F : ℕ 0 ⟶ K
121 fzo0ssnn0 ⊢ 0 ..^ 3 ⊆ ℕ 0
122 78 121 eqsstrrdi ⊢ φ → 0 1 2 ⊆ ℕ 0
123 122 sselda ⊢ φ ∧ k ∈ 0 1 2 → k ∈ ℕ 0
124 120 123 ffvelcdmd ⊢ φ ∧ k ∈ 0 1 2 → F ⁡ k ∈ K
125 123 39 syldan ⊢ φ ∧ k ∈ 0 1 2 → k × ˙ X ∈ K
126 3 5 117 124 125 ringcld ⊢ φ ∧ k ∈ 0 1 2 → F ⁡ k · ˙ k × ˙ X ∈ K
127 126 fmpttd ⊢ φ → k ∈ 0 1 2 ⟼ F ⁡ k · ˙ k × ˙ X : 0 1 2 ⟶ K
128 fzofi ⊢ 0 ..^ 3 ∈ Fin
129 78 128 eqeltrrdi ⊢ φ → 0 1 2 ∈ Fin
130 127 129 41 fidmfisupp ⊢ φ → finSupp 0 R⁡ k ∈ 0 1 2 ⟼ F ⁡ k · ˙ k × ˙ X
131 3 24 26 116 127 130 gsumcl ⊢ φ → ∑ R k ∈ 0 1 2 F ⁡ k · ˙ k × ˙ X ∈ K
132 3 6 24 108 131 grpridd ⊢ φ → ∑ R k ∈ 0 1 2 F ⁡ k · ˙ k × ˙ X + ˙ 0 R = ∑ R k ∈ 0 1 2 F ⁡ k · ˙ k × ˙ X
133 fveq2 ⊢ k = 0 → F ⁡ k = F ⁡ 0
134 133 12 eqtr4di ⊢ k = 0 → F ⁡ k = C
135 oveq1 ⊢ k = 0 → k × ˙ X = 0 × ˙ X
136 134 135 oveq12d ⊢ k = 0 → F ⁡ k · ˙ k × ˙ X = C · ˙ 0 × ˙ X
137 fveq2 ⊢ k = 1 → F ⁡ k = F ⁡ 1
138 137 11 eqtr4di ⊢ k = 1 → F ⁡ k = B
139 oveq1 ⊢ k = 1 → k × ˙ X = 1 × ˙ X
140 138 139 oveq12d ⊢ k = 1 → F ⁡ k · ˙ k × ˙ X = B · ˙ 1 × ˙ X
141 fveq2 ⊢ k = 2 → F ⁡ k = F ⁡ 2
142 141 10 eqtr4di ⊢ k = 2 → F ⁡ k = A
143 oveq1 ⊢ k = 2 → k × ˙ X = 2 × ˙ X
144 142 143 oveq12d ⊢ k = 2 → F ⁡ k · ˙ k × ˙ X = A · ˙ 2 × ˙ X
145 0nn0 ⊢ 0 ∈ ℕ 0
146 145 a1i ⊢ φ → 0 ∈ ℕ 0
147 1nn0 ⊢ 1 ∈ ℕ 0
148 147 a1i ⊢ φ → 1 ∈ ℕ 0
149 0ne1 ⊢ 0 ≠ 1
150 149 a1i ⊢ φ → 0 ≠ 1
151 1ne2 ⊢ 1 ≠ 2
152 151 a1i ⊢ φ → 1 ≠ 2
153 0ne2 ⊢ 0 ≠ 2
154 153 a1i ⊢ φ → 0 ≠ 2
155 8 4 1 3 coe1fvalcl ⊢ M ∈ U ∧ 0 ∈ ℕ 0 → F ⁡ 0 ∈ K
156 14 145 155 sylancl ⊢ φ → F ⁡ 0 ∈ K
157 12 156 eqeltrid ⊢ φ → C ∈ K
158 33 7 35 146 16 mulgnn0cld ⊢ φ → 0 × ˙ X ∈ K
159 3 5 25 157 158 ringcld ⊢ φ → C · ˙ 0 × ˙ X ∈ K
160 8 4 1 3 coe1fvalcl ⊢ M ∈ U ∧ 1 ∈ ℕ 0 → F ⁡ 1 ∈ K
161 14 147 160 sylancl ⊢ φ → F ⁡ 1 ∈ K
162 11 161 eqeltrid ⊢ φ → B ∈ K
163 33 7 35 148 16 mulgnn0cld ⊢ φ → 1 × ˙ X ∈ K
164 3 5 25 162 163 ringcld ⊢ φ → B · ˙ 1 × ˙ X ∈ K
165 8 4 1 3 coe1fvalcl ⊢ M ∈ U ∧ 2 ∈ ℕ 0 → F ⁡ 2 ∈ K
166 14 48 165 sylancl ⊢ φ → F ⁡ 2 ∈ K
167 10 166 eqeltrid ⊢ φ → A ∈ K
168 33 7 35 49 16 mulgnn0cld ⊢ φ → 2 × ˙ X ∈ K
169 3 5 25 167 168 ringcld ⊢ φ → A · ˙ 2 × ˙ X ∈ K
170 3 6 136 140 144 26 146 148 49 150 152 154 159 164 169 gsumtp ⊢ φ → ∑ R k ∈ 0 1 2 F ⁡ k · ˙ k × ˙ X = C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X + ˙ A · ˙ 2 × ˙ X
171 3 6 108 159 164 grpcld ⊢ φ → C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X ∈ K
172 3 6 cmncom ⊢ R ∈ CMnd ∧ C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X ∈ K ∧ A · ˙ 2 × ˙ X ∈ K → C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X + ˙ A · ˙ 2 × ˙ X = A · ˙ 2 × ˙ X + ˙ C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X
173 26 171 169 172 syl3anc ⊢ φ → C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X + ˙ A · ˙ 2 × ˙ X = A · ˙ 2 × ˙ X + ˙ C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X
174 3 6 cmncom ⊢ R ∈ CMnd ∧ C · ˙ 0 × ˙ X ∈ K ∧ B · ˙ 1 × ˙ X ∈ K → C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X = B · ˙ 1 × ˙ X + ˙ C · ˙ 0 × ˙ X
175 26 159 164 174 syl3anc ⊢ φ → C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X = B · ˙ 1 × ˙ X + ˙ C · ˙ 0 × ˙ X
176 33 7 mulg1 ⊢ X ∈ K → 1 × ˙ X = X
177 16 176 syl ⊢ φ → 1 × ˙ X = X
178 177 oveq2d ⊢ φ → B · ˙ 1 × ˙ X = B · ˙ X
179 eqid ⊢ 1 R = 1 R
180 32 179 ringidval ⊢ 1 R = 0 mulGrp R
181 33 180 7 mulg0 ⊢ X ∈ K → 0 × ˙ X = 1 R
182 16 181 syl ⊢ φ → 0 × ˙ X = 1 R
183 182 oveq2d ⊢ φ → C · ˙ 0 × ˙ X = C · ˙ 1 R
184 3 5 179 25 157 ringridmd ⊢ φ → C · ˙ 1 R = C
185 183 184 eqtrd ⊢ φ → C · ˙ 0 × ˙ X = C
186 178 185 oveq12d ⊢ φ → B · ˙ 1 × ˙ X + ˙ C · ˙ 0 × ˙ X = B · ˙ X + ˙ C
187 175 186 eqtrd ⊢ φ → C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X = B · ˙ X + ˙ C
188 187 oveq2d ⊢ φ → A · ˙ 2 × ˙ X + ˙ C · ˙ 0 × ˙ X + ˙ B · ˙ 1 × ˙ X = A · ˙ 2 × ˙ X + ˙ B · ˙ X + ˙ C
189 170 173 188 3eqtrd ⊢ φ → ∑ R k ∈ 0 1 2 F ⁡ k · ˙ k × ˙ X = A · ˙ 2 × ˙ X + ˙ B · ˙ X + ˙ C
190 114 132 189 3eqtrd ⊢ φ → ∑ R k ∈ 0 ..^ 3 F ⁡ k · ˙ k × ˙ X + ˙ ∑ R k ∈ ℤ ≥ 3 F ⁡ k · ˙ k × ˙ X = A · ˙ 2 × ˙ X + ˙ B · ˙ X + ˙ C
191 23 76 190 3eqtrd ⊢ φ → O ⁡ M ⁡ X = A · ˙ 2 × ˙ X + ˙ B · ˙ X + ˙ C