Metamath Proof Explorer


Theorem fiint

Description: Equivalent ways of stating the finite intersection property. We show two ways of saying, "the intersection of elements in every finite nonempty subcollection of A is in A ". This theorem is applicable to a topology, which (among other axioms) is closed under finite intersections. Some texts use the left-hand version of this axiom and others the right-hand version, but as our proof here shows, their "intuitively obvious" equivalence can be non-trivial to establish formally. (Contributed by NM, 22-Sep-2002) Use a separate setvar for the right-hand side and avoid ax-pow . (Revised by BTernaryTau, 14-Jan-2025)

Ref Expression
Assertion fiint x A y A x y A z z A z z Fin z A

Proof

Step Hyp Ref Expression
1 isfi z Fin w ω z w
2 nnfi w ω w Fin
3 ensymfib w Fin w z z w
4 2 3 syl w ω w z z w
5 breq1 w = w z z
6 5 anbi2d w = z A z w z z A z z
7 6 imbi1d w = z A z w z z A z A z z z A
8 7 albidv w = z z A z w z z A z z A z z z A
9 breq1 w = t w z t z
10 9 anbi2d w = t z A z w z z A z t z
11 10 imbi1d w = t z A z w z z A z A z t z z A
12 11 albidv w = t z z A z w z z A z z A z t z z A
13 breq1 w = suc t w z suc t z
14 13 anbi2d w = suc t z A z w z z A z suc t z
15 14 imbi1d w = suc t z A z w z z A z A z suc t z z A
16 15 albidv w = suc t z z A z w z z A z z A z suc t z z A
17 en0r z z =
18 17 biimpi z z =
19 18 anim1i z z z = z
20 19 ancoms z z z = z
21 20 adantll z A z z z = z
22 df-ne z ¬ z =
23 pm3.24 ¬ z = ¬ z =
24 23 pm2.21i z = ¬ z = z A
25 22 24 sylan2b z = z z A
26 21 25 syl z A z z z A
27 26 ax-gen z z A z z z A
28 27 a1i v A u A v u A z z A z z z A
29 nfv z v A u A v u A
30 nfa1 z z z A z t z z A
31 bren suc t z f f : suc t 1-1 onto z
32 ssel z A f t z f t A
33 f1of f : suc t 1-1 onto z f : suc t z
34 vex t V
35 34 sucid t suc t
36 ffvelcdm f : suc t z t suc t f t z
37 33 35 36 sylancl f : suc t 1-1 onto z f t z
38 32 37 impel z A f : suc t 1-1 onto z f t A
39 38 adantr z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A f t A
40 df-ne f t ¬ f t =
41 imassrn f t ran f
42 dff1o2 f : suc t 1-1 onto z f Fn suc t Fun f -1 ran f = z
43 42 simp3bi f : suc t 1-1 onto z ran f = z
44 41 43 sseqtrid f : suc t 1-1 onto z f t z
45 sstr2 f t z z A f t A
46 44 45 syl f : suc t 1-1 onto z z A f t A
47 46 anim1d f : suc t 1-1 onto z z A f t f t A f t
48 f1of1 f : suc t 1-1 onto z f : suc t 1-1 z
49 sssucid t suc t
50 vex f V
51 f1imaen3g f : suc t 1-1 z t suc t f V t f t
52 49 50 51 mp3an23 f : suc t 1-1 z t f t
53 48 52 syl f : suc t 1-1 onto z t f t
54 47 53 jctird f : suc t 1-1 onto z z A f t f t A f t t f t
55 50 imaex f t V
56 sseq1 z = f t z A f t A
57 neeq1 z = f t z f t
58 56 57 anbi12d z = f t z A z f t A f t
59 breq2 z = f t t z t f t
60 58 59 anbi12d z = f t z A z t z f t A f t t f t
61 inteq z = f t z = f t
62 61 eleq1d z = f t z A f t A
63 60 62 imbi12d z = f t z A z t z z A f t A f t t f t f t A
64 55 63 spcv z z A z t z z A f t A f t t f t f t A
65 54 64 sylan9 f : suc t 1-1 onto z z z A z t z z A z A f t f t A
66 ineq1 v = f t v u = f t u
67 66 eleq1d v = f t v u A f t u A
68 ineq2 u = f t f t u = f t f t
69 68 eleq1d u = f t f t u A f t f t A
70 67 69 rspc2v f t A f t A v A u A v u A f t f t A
71 70 ex f t A f t A v A u A v u A f t f t A
72 65 71 syl6 f : suc t 1-1 onto z z z A z t z z A z A f t f t A v A u A v u A f t f t A
73 72 com4r v A u A v u A f : suc t 1-1 onto z z z A z t z z A z A f t f t A f t f t A
74 73 exp5c v A u A v u A f : suc t 1-1 onto z z z A z t z z A z A f t f t A f t f t A
75 74 com14 z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A f t f t A f t f t A
76 75 imp43 z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A f t f t A f t f t A
77 40 76 biimtrrid z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A ¬ f t = f t A f t f t A
78 inteq f t = f t =
79 int0 = V
80 78 79 eqtrdi f t = f t = V
81 80 ineq1d f t = f t f t = V f t
82 ssv f t V
83 sseqin2 f t V V f t = f t
84 82 83 mpbi V f t = f t
85 81 84 eqtrdi f t = f t f t = f t
86 85 eleq1d f t = f t f t A f t A
87 86 biimprd f t = f t A f t f t A
88 77 87 pm2.61d2 z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A f t A f t f t A
89 39 88 mpd z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A f t f t A
90 fvex f t V
91 90 intunsn f t f t = f t f t
92 f1ofn f : suc t 1-1 onto z f Fn suc t
93 fnsnfv f Fn suc t t suc t f t = f t
94 92 35 93 sylancl f : suc t 1-1 onto z f t = f t
95 94 uneq2d f : suc t 1-1 onto z f t f t = f t f t
96 df-suc suc t = t t
97 96 imaeq2i f suc t = f t t
98 imaundi f t t = f t f t
99 97 98 eqtr2i f t f t = f suc t
100 95 99 eqtrdi f : suc t 1-1 onto z f t f t = f suc t
101 f1ofo f : suc t 1-1 onto z f : suc t onto z
102 foima f : suc t onto z f suc t = z
103 101 102 syl f : suc t 1-1 onto z f suc t = z
104 100 103 eqtrd f : suc t 1-1 onto z f t f t = z
105 104 inteqd f : suc t 1-1 onto z f t f t = z
106 91 105 eqtr3id f : suc t 1-1 onto z f t f t = z
107 106 eleq1d f : suc t 1-1 onto z f t f t A z A
108 107 ad2antlr z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A f t f t A z A
109 89 108 mpbid z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A z A
110 109 exp43 z A f : suc t 1-1 onto z z z A z t z z A v A u A v u A z A
111 110 exlimdv z A f f : suc t 1-1 onto z z z A z t z z A v A u A v u A z A
112 31 111 biimtrid z A suc t z z z A z t z z A v A u A v u A z A
113 112 imp z A suc t z z z A z t z z A v A u A v u A z A
114 113 adantlr z A z suc t z z z A z t z z A v A u A v u A z A
115 114 com13 v A u A v u A z z A z t z z A z A z suc t z z A
116 29 30 115 alrimd v A u A v u A z z A z t z z A z z A z suc t z z A
117 116 a1i t ω v A u A v u A z z A z t z z A z z A z suc t z z A
118 8 12 16 28 117 finds2 w ω v A u A v u A z z A z w z z A
119 sp z z A z w z z A z A z w z z A
120 118 119 syl6 w ω v A u A v u A z A z w z z A
121 120 exp4a w ω v A u A v u A z A z w z z A
122 121 com24 w ω w z z A z v A u A v u A z A
123 4 122 sylbird w ω z w z A z v A u A v u A z A
124 123 rexlimiv w ω z w z A z v A u A v u A z A
125 1 124 sylbi z Fin z A z v A u A v u A z A
126 125 com13 v A u A v u A z A z z Fin z A
127 126 impd v A u A v u A z A z z Fin z A
128 127 alrimiv v A u A v u A z z A z z Fin z A
129 zfpair2 v u V
130 sseq1 z = v u z A v u A
131 neeq1 z = v u z v u
132 130 131 anbi12d z = v u z A z v u A v u
133 eleq1 z = v u z Fin v u Fin
134 132 133 anbi12d z = v u z A z z Fin v u A v u v u Fin
135 inteq z = v u z = v u
136 135 eleq1d z = v u z A v u A
137 134 136 imbi12d z = v u z A z z Fin z A v u A v u v u Fin v u A
138 129 137 spcv z z A z z Fin z A v u A v u v u Fin v u A
139 vex v V
140 vex u V
141 139 140 prss v A u A v u A
142 139 prnz v u
143 142 biantru v u A v u A v u
144 prfi v u Fin
145 144 biantru v u A v u v u A v u v u Fin
146 141 143 145 3bitrri v u A v u v u Fin v A u A
147 139 140 intpr v u = v u
148 147 eleq1i v u A v u A
149 138 146 148 3imtr3g z z A z z Fin z A v A u A v u A
150 149 ralrimivv z z A z z Fin z A v A u A v u A
151 128 150 impbii v A u A v u A z z A z z Fin z A
152 ineq1 x = v x y = v y
153 152 eleq1d x = v x y A v y A
154 ineq2 y = u v y = v u
155 154 eleq1d y = u v y A v u A
156 153 155 cbvral2vw x A y A x y A v A u A v u A
157 df-3an z A z z Fin z A z z Fin
158 157 imbi1i z A z z Fin z A z A z z Fin z A
159 158 albii z z A z z Fin z A z z A z z Fin z A
160 151 156 159 3bitr4i x A y A x y A z z A z z Fin z A