Metamath Proof Explorer


Theorem smfmullem2

Description: The multiplication of two sigma-measurable functions is measurable: this is the step (i) of the proof of Proposition 121E (d) of Fremlin1 p. 37 . (Contributed by Glauco Siliprandi, 26-Jun-2021)

Ref Expression
Hypotheses smfmullem2.a
|- ( ph -> A e. RR )
smfmullem2.k
|- K = { q e. ( QQ ^m ( 0 ... 3 ) ) | A. u e. ( ( q ` 0 ) (,) ( q ` 1 ) ) A. v e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ( u x. v ) < A }
smfmullem2.u
|- ( ph -> U e. RR )
smfmullem2.v
|- ( ph -> V e. RR )
smfmullem2.l
|- ( ph -> ( U x. V ) < A )
smfmullem2.p
|- ( ph -> P e. QQ )
smfmullem2.r
|- ( ph -> R e. QQ )
smfmullem2.s
|- ( ph -> S e. QQ )
smfmullem2.z
|- ( ph -> Z e. QQ )
smfmullem2.p2
|- ( ph -> P e. ( ( U - Y ) (,) U ) )
smfmullem2.42
|- ( ph -> R e. ( U (,) ( U + Y ) ) )
smfmullem2.w2
|- ( ph -> S e. ( ( V - Y ) (,) V ) )
smfmullem2.z2
|- ( ph -> Z e. ( V (,) ( V + Y ) ) )
smfmullem2.x
|- X = ( ( A - ( U x. V ) ) / ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) )
smfmullem2.y
|- Y = if ( 1 <_ X , 1 , X )
Assertion smfmullem2
|- ( ph -> E. q e. K ( U e. ( ( q ` 0 ) (,) ( q ` 1 ) ) /\ V e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ) )

Proof

Step Hyp Ref Expression
1 smfmullem2.a
 |-  ( ph -> A e. RR )
2 smfmullem2.k
 |-  K = { q e. ( QQ ^m ( 0 ... 3 ) ) | A. u e. ( ( q ` 0 ) (,) ( q ` 1 ) ) A. v e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ( u x. v ) < A }
3 smfmullem2.u
 |-  ( ph -> U e. RR )
4 smfmullem2.v
 |-  ( ph -> V e. RR )
5 smfmullem2.l
 |-  ( ph -> ( U x. V ) < A )
6 smfmullem2.p
 |-  ( ph -> P e. QQ )
7 smfmullem2.r
 |-  ( ph -> R e. QQ )
8 smfmullem2.s
 |-  ( ph -> S e. QQ )
9 smfmullem2.z
 |-  ( ph -> Z e. QQ )
10 smfmullem2.p2
 |-  ( ph -> P e. ( ( U - Y ) (,) U ) )
11 smfmullem2.42
 |-  ( ph -> R e. ( U (,) ( U + Y ) ) )
12 smfmullem2.w2
 |-  ( ph -> S e. ( ( V - Y ) (,) V ) )
13 smfmullem2.z2
 |-  ( ph -> Z e. ( V (,) ( V + Y ) ) )
14 smfmullem2.x
 |-  X = ( ( A - ( U x. V ) ) / ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) )
15 smfmullem2.y
 |-  Y = if ( 1 <_ X , 1 , X )
16 6 7 8 9 s4cld
 |-  ( ph -> <" P R S Z "> e. Word QQ )
17 s4len
 |-  ( # ` <" P R S Z "> ) = 4
18 17 a1i
 |-  ( ph -> ( # ` <" P R S Z "> ) = 4 )
19 16 18 jca
 |-  ( ph -> ( <" P R S Z "> e. Word QQ /\ ( # ` <" P R S Z "> ) = 4 ) )
20 qex
 |-  QQ e. _V
21 20 a1i
 |-  ( ph -> QQ e. _V )
22 4nn0
 |-  4 e. NN0
23 22 a1i
 |-  ( ph -> 4 e. NN0 )
24 wrdmap
 |-  ( ( QQ e. _V /\ 4 e. NN0 ) -> ( ( <" P R S Z "> e. Word QQ /\ ( # ` <" P R S Z "> ) = 4 ) <-> <" P R S Z "> e. ( QQ ^m ( 0 ..^ 4 ) ) ) )
25 21 23 24 syl2anc
 |-  ( ph -> ( ( <" P R S Z "> e. Word QQ /\ ( # ` <" P R S Z "> ) = 4 ) <-> <" P R S Z "> e. ( QQ ^m ( 0 ..^ 4 ) ) ) )
26 19 25 mpbid
 |-  ( ph -> <" P R S Z "> e. ( QQ ^m ( 0 ..^ 4 ) ) )
27 3z
 |-  3 e. ZZ
28 fzval3
 |-  ( 3 e. ZZ -> ( 0 ... 3 ) = ( 0 ..^ ( 3 + 1 ) ) )
29 27 28 ax-mp
 |-  ( 0 ... 3 ) = ( 0 ..^ ( 3 + 1 ) )
30 3p1e4
 |-  ( 3 + 1 ) = 4
31 30 oveq2i
 |-  ( 0 ..^ ( 3 + 1 ) ) = ( 0 ..^ 4 )
32 29 31 eqtri
 |-  ( 0 ... 3 ) = ( 0 ..^ 4 )
33 32 eqcomi
 |-  ( 0 ..^ 4 ) = ( 0 ... 3 )
34 33 a1i
 |-  ( ph -> ( 0 ..^ 4 ) = ( 0 ... 3 ) )
35 34 oveq2d
 |-  ( ph -> ( QQ ^m ( 0 ..^ 4 ) ) = ( QQ ^m ( 0 ... 3 ) ) )
36 26 35 eleqtrd
 |-  ( ph -> <" P R S Z "> e. ( QQ ^m ( 0 ... 3 ) ) )
37 simpr
 |-  ( ( ph /\ u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) ) -> u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) )
38 s4fv0
 |-  ( P e. QQ -> ( <" P R S Z "> ` 0 ) = P )
39 6 38 syl
 |-  ( ph -> ( <" P R S Z "> ` 0 ) = P )
40 s4fv1
 |-  ( R e. QQ -> ( <" P R S Z "> ` 1 ) = R )
41 7 40 syl
 |-  ( ph -> ( <" P R S Z "> ` 1 ) = R )
42 39 41 oveq12d
 |-  ( ph -> ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) = ( P (,) R ) )
43 42 adantr
 |-  ( ( ph /\ u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) ) -> ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) = ( P (,) R ) )
44 37 43 eleqtrd
 |-  ( ( ph /\ u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) ) -> u e. ( P (,) R ) )
45 simpr
 |-  ( ( ph /\ v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) -> v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) )
46 s4fv2
 |-  ( S e. QQ -> ( <" P R S Z "> ` 2 ) = S )
47 8 46 syl
 |-  ( ph -> ( <" P R S Z "> ` 2 ) = S )
48 s4fv3
 |-  ( Z e. QQ -> ( <" P R S Z "> ` 3 ) = Z )
49 9 48 syl
 |-  ( ph -> ( <" P R S Z "> ` 3 ) = Z )
50 47 49 oveq12d
 |-  ( ph -> ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) = ( S (,) Z ) )
51 50 adantr
 |-  ( ( ph /\ v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) -> ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) = ( S (,) Z ) )
52 45 51 eleqtrd
 |-  ( ( ph /\ v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) -> v e. ( S (,) Z ) )
53 simpr
 |-  ( ( ph /\ v e. ( S (,) Z ) ) -> v e. ( S (,) Z ) )
54 52 53 syldan
 |-  ( ( ph /\ v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) -> v e. ( S (,) Z ) )
55 54 adantlr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) -> v e. ( S (,) Z ) )
56 1 ad2antrr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> A e. RR )
57 3 ad2antrr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> U e. RR )
58 4 ad2antrr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> V e. RR )
59 5 ad2antrr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> ( U x. V ) < A )
60 10 ad2antrr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> P e. ( ( U - Y ) (,) U ) )
61 11 ad2antrr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> R e. ( U (,) ( U + Y ) ) )
62 12 ad2antrr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> S e. ( ( V - Y ) (,) V ) )
63 13 ad2antrr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> Z e. ( V (,) ( V + Y ) ) )
64 simplr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> u e. ( P (,) R ) )
65 simpr
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> v e. ( S (,) Z ) )
66 56 57 58 59 14 15 60 61 62 63 64 65 smfmullem1
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( S (,) Z ) ) -> ( u x. v ) < A )
67 55 66 syldan
 |-  ( ( ( ph /\ u e. ( P (,) R ) ) /\ v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) -> ( u x. v ) < A )
68 67 ralrimiva
 |-  ( ( ph /\ u e. ( P (,) R ) ) -> A. v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ( u x. v ) < A )
69 44 68 syldan
 |-  ( ( ph /\ u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) ) -> A. v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ( u x. v ) < A )
70 69 ralrimiva
 |-  ( ph -> A. u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) A. v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ( u x. v ) < A )
71 36 70 jca
 |-  ( ph -> ( <" P R S Z "> e. ( QQ ^m ( 0 ... 3 ) ) /\ A. u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) A. v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ( u x. v ) < A ) )
72 fveq1
 |-  ( q = <" P R S Z "> -> ( q ` 0 ) = ( <" P R S Z "> ` 0 ) )
73 fveq1
 |-  ( q = <" P R S Z "> -> ( q ` 1 ) = ( <" P R S Z "> ` 1 ) )
74 72 73 oveq12d
 |-  ( q = <" P R S Z "> -> ( ( q ` 0 ) (,) ( q ` 1 ) ) = ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) )
75 74 raleqdv
 |-  ( q = <" P R S Z "> -> ( A. u e. ( ( q ` 0 ) (,) ( q ` 1 ) ) A. v e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ( u x. v ) < A <-> A. u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) A. v e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ( u x. v ) < A ) )
76 fveq1
 |-  ( q = <" P R S Z "> -> ( q ` 2 ) = ( <" P R S Z "> ` 2 ) )
77 fveq1
 |-  ( q = <" P R S Z "> -> ( q ` 3 ) = ( <" P R S Z "> ` 3 ) )
78 76 77 oveq12d
 |-  ( q = <" P R S Z "> -> ( ( q ` 2 ) (,) ( q ` 3 ) ) = ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) )
79 78 raleqdv
 |-  ( q = <" P R S Z "> -> ( A. v e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ( u x. v ) < A <-> A. v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ( u x. v ) < A ) )
80 79 ralbidv
 |-  ( q = <" P R S Z "> -> ( A. u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) A. v e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ( u x. v ) < A <-> A. u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) A. v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ( u x. v ) < A ) )
81 75 80 bitrd
 |-  ( q = <" P R S Z "> -> ( A. u e. ( ( q ` 0 ) (,) ( q ` 1 ) ) A. v e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ( u x. v ) < A <-> A. u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) A. v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ( u x. v ) < A ) )
82 81 2 elrab2
 |-  ( <" P R S Z "> e. K <-> ( <" P R S Z "> e. ( QQ ^m ( 0 ... 3 ) ) /\ A. u e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) A. v e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ( u x. v ) < A ) )
83 71 82 sylibr
 |-  ( ph -> <" P R S Z "> e. K )
84 qssre
 |-  QQ C_ RR
85 84 6 sseldi
 |-  ( ph -> P e. RR )
86 85 rexrd
 |-  ( ph -> P e. RR* )
87 84 7 sseldi
 |-  ( ph -> R e. RR )
88 87 rexrd
 |-  ( ph -> R e. RR* )
89 15 a1i
 |-  ( ph -> Y = if ( 1 <_ X , 1 , X ) )
90 1rp
 |-  1 e. RR+
91 90 a1i
 |-  ( ph -> 1 e. RR+ )
92 14 a1i
 |-  ( ph -> X = ( ( A - ( U x. V ) ) / ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) ) )
93 3 4 remulcld
 |-  ( ph -> ( U x. V ) e. RR )
94 difrp
 |-  ( ( ( U x. V ) e. RR /\ A e. RR ) -> ( ( U x. V ) < A <-> ( A - ( U x. V ) ) e. RR+ ) )
95 93 1 94 syl2anc
 |-  ( ph -> ( ( U x. V ) < A <-> ( A - ( U x. V ) ) e. RR+ ) )
96 5 95 mpbid
 |-  ( ph -> ( A - ( U x. V ) ) e. RR+ )
97 1red
 |-  ( ph -> 1 e. RR )
98 3 recnd
 |-  ( ph -> U e. CC )
99 98 abscld
 |-  ( ph -> ( abs ` U ) e. RR )
100 4 recnd
 |-  ( ph -> V e. CC )
101 100 abscld
 |-  ( ph -> ( abs ` V ) e. RR )
102 99 101 readdcld
 |-  ( ph -> ( ( abs ` U ) + ( abs ` V ) ) e. RR )
103 97 102 readdcld
 |-  ( ph -> ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) e. RR )
104 0re
 |-  0 e. RR
105 104 a1i
 |-  ( ph -> 0 e. RR )
106 91 rpgt0d
 |-  ( ph -> 0 < 1 )
107 98 absge0d
 |-  ( ph -> 0 <_ ( abs ` U ) )
108 100 absge0d
 |-  ( ph -> 0 <_ ( abs ` V ) )
109 99 101 addge01d
 |-  ( ph -> ( 0 <_ ( abs ` V ) <-> ( abs ` U ) <_ ( ( abs ` U ) + ( abs ` V ) ) ) )
110 108 109 mpbid
 |-  ( ph -> ( abs ` U ) <_ ( ( abs ` U ) + ( abs ` V ) ) )
111 105 99 102 107 110 letrd
 |-  ( ph -> 0 <_ ( ( abs ` U ) + ( abs ` V ) ) )
112 97 102 addge01d
 |-  ( ph -> ( 0 <_ ( ( abs ` U ) + ( abs ` V ) ) <-> 1 <_ ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) ) )
113 111 112 mpbid
 |-  ( ph -> 1 <_ ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) )
114 105 97 103 106 113 ltletrd
 |-  ( ph -> 0 < ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) )
115 103 114 elrpd
 |-  ( ph -> ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) e. RR+ )
116 96 115 rpdivcld
 |-  ( ph -> ( ( A - ( U x. V ) ) / ( 1 + ( ( abs ` U ) + ( abs ` V ) ) ) ) e. RR+ )
117 92 116 eqeltrd
 |-  ( ph -> X e. RR+ )
118 91 117 ifcld
 |-  ( ph -> if ( 1 <_ X , 1 , X ) e. RR+ )
119 89 118 eqeltrd
 |-  ( ph -> Y e. RR+ )
120 119 rpred
 |-  ( ph -> Y e. RR )
121 3 120 resubcld
 |-  ( ph -> ( U - Y ) e. RR )
122 121 rexrd
 |-  ( ph -> ( U - Y ) e. RR* )
123 3 rexrd
 |-  ( ph -> U e. RR* )
124 iooltub
 |-  ( ( ( U - Y ) e. RR* /\ U e. RR* /\ P e. ( ( U - Y ) (,) U ) ) -> P < U )
125 122 123 10 124 syl3anc
 |-  ( ph -> P < U )
126 3 120 readdcld
 |-  ( ph -> ( U + Y ) e. RR )
127 126 rexrd
 |-  ( ph -> ( U + Y ) e. RR* )
128 ioogtlb
 |-  ( ( U e. RR* /\ ( U + Y ) e. RR* /\ R e. ( U (,) ( U + Y ) ) ) -> U < R )
129 123 127 11 128 syl3anc
 |-  ( ph -> U < R )
130 86 88 3 125 129 eliood
 |-  ( ph -> U e. ( P (,) R ) )
131 42 eqcomd
 |-  ( ph -> ( P (,) R ) = ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) )
132 130 131 eleqtrd
 |-  ( ph -> U e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) )
133 84 8 sseldi
 |-  ( ph -> S e. RR )
134 133 rexrd
 |-  ( ph -> S e. RR* )
135 84 9 sseldi
 |-  ( ph -> Z e. RR )
136 135 rexrd
 |-  ( ph -> Z e. RR* )
137 4 120 resubcld
 |-  ( ph -> ( V - Y ) e. RR )
138 137 rexrd
 |-  ( ph -> ( V - Y ) e. RR* )
139 4 rexrd
 |-  ( ph -> V e. RR* )
140 iooltub
 |-  ( ( ( V - Y ) e. RR* /\ V e. RR* /\ S e. ( ( V - Y ) (,) V ) ) -> S < V )
141 138 139 12 140 syl3anc
 |-  ( ph -> S < V )
142 4 120 readdcld
 |-  ( ph -> ( V + Y ) e. RR )
143 142 rexrd
 |-  ( ph -> ( V + Y ) e. RR* )
144 ioogtlb
 |-  ( ( V e. RR* /\ ( V + Y ) e. RR* /\ Z e. ( V (,) ( V + Y ) ) ) -> V < Z )
145 139 143 13 144 syl3anc
 |-  ( ph -> V < Z )
146 134 136 4 141 145 eliood
 |-  ( ph -> V e. ( S (,) Z ) )
147 50 eqcomd
 |-  ( ph -> ( S (,) Z ) = ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) )
148 146 147 eleqtrd
 |-  ( ph -> V e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) )
149 132 148 jca
 |-  ( ph -> ( U e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) /\ V e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) )
150 nfv
 |-  F/ q ( U e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) /\ V e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) )
151 nfcv
 |-  F/_ q <" P R S Z ">
152 nfrab1
 |-  F/_ q { q e. ( QQ ^m ( 0 ... 3 ) ) | A. u e. ( ( q ` 0 ) (,) ( q ` 1 ) ) A. v e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ( u x. v ) < A }
153 2 152 nfcxfr
 |-  F/_ q K
154 74 eleq2d
 |-  ( q = <" P R S Z "> -> ( U e. ( ( q ` 0 ) (,) ( q ` 1 ) ) <-> U e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) ) )
155 78 eleq2d
 |-  ( q = <" P R S Z "> -> ( V e. ( ( q ` 2 ) (,) ( q ` 3 ) ) <-> V e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) )
156 154 155 anbi12d
 |-  ( q = <" P R S Z "> -> ( ( U e. ( ( q ` 0 ) (,) ( q ` 1 ) ) /\ V e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ) <-> ( U e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) /\ V e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) ) )
157 150 151 153 156 rspcef
 |-  ( ( <" P R S Z "> e. K /\ ( U e. ( ( <" P R S Z "> ` 0 ) (,) ( <" P R S Z "> ` 1 ) ) /\ V e. ( ( <" P R S Z "> ` 2 ) (,) ( <" P R S Z "> ` 3 ) ) ) ) -> E. q e. K ( U e. ( ( q ` 0 ) (,) ( q ` 1 ) ) /\ V e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ) )
158 83 149 157 syl2anc
 |-  ( ph -> E. q e. K ( U e. ( ( q ` 0 ) (,) ( q ` 1 ) ) /\ V e. ( ( q ` 2 ) (,) ( q ` 3 ) ) ) )