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isbasisrelowllem2
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Ascii
Unicode
Theorem
isbasisrelowllem2
Description:
Lemma for
isbasisrelowl
.
(Contributed by
ML
, 27-Jul-2020)
Ref
Expression
Hypothesis
isbasisrelowl.1
⊢
I
=
.
ℝ
2
Assertion
isbasisrelowllem2
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
x
∩
y
∈
I
Proof
Step
Hyp
Ref
Expression
1
isbasisrelowl.1
⊢
I
=
.
ℝ
2
2
simplr1
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
c
∈
ℝ
3
simplr2
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
d
∈
ℝ
4
nfv
⊢
Ⅎ
z
a
∈
ℝ
5
nfv
⊢
Ⅎ
z
b
∈
ℝ
6
nfrab1
⊢
Ⅎ
_
z
z
∈
ℝ
|
a
≤
z
∧
z
<
b
7
6
nfeq2
⊢
Ⅎ
z
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
8
4
5
7
nf3an
⊢
Ⅎ
z
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
9
nfv
⊢
Ⅎ
z
c
∈
ℝ
10
nfv
⊢
Ⅎ
z
d
∈
ℝ
11
nfrab1
⊢
Ⅎ
_
z
z
∈
ℝ
|
c
≤
z
∧
z
<
d
12
11
nfeq2
⊢
Ⅎ
z
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
13
9
10
12
nf3an
⊢
Ⅎ
z
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
14
8
13
nfan
⊢
Ⅎ
z
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
15
nfv
⊢
Ⅎ
z
a
≤
c
∧
d
≤
b
16
14
15
nfan
⊢
Ⅎ
z
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
17
nfcv
⊢
Ⅎ
_
z
x
∩
y
18
simp3
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
→
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
19
simp3
⊢
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
20
elin
⊢
z
∈
x
∩
y
↔
z
∈
x
∧
z
∈
y
21
eleq2
⊢
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
→
z
∈
x
↔
z
∈
z
∈
ℝ
|
a
≤
z
∧
z
<
b
22
rabid
⊢
z
∈
z
∈
ℝ
|
a
≤
z
∧
z
<
b
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
23
21
22
bitrdi
⊢
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
→
z
∈
x
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
24
23
anbi1d
⊢
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
→
z
∈
x
∧
z
∈
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
z
∈
y
25
20
24
bitrid
⊢
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
→
z
∈
x
∩
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
z
∈
y
26
eleq2
⊢
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
z
∈
y
↔
z
∈
z
∈
ℝ
|
c
≤
z
∧
z
<
d
27
rabid
⊢
z
∈
z
∈
ℝ
|
c
≤
z
∧
z
<
d
↔
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
28
26
27
bitrdi
⊢
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
z
∈
y
↔
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
29
28
anbi2d
⊢
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
z
∈
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
30
25
29
sylan9bb
⊢
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
z
∈
x
∩
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
31
an4
⊢
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
↔
z
∈
ℝ
∧
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
32
anidm
⊢
z
∈
ℝ
∧
z
∈
ℝ
↔
z
∈
ℝ
33
32
anbi1i
⊢
z
∈
ℝ
∧
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
34
31
33
bitri
⊢
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
35
an4
⊢
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
↔
a
≤
z
∧
c
≤
z
∧
z
<
d
∧
z
<
b
36
an42
⊢
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
↔
a
≤
z
∧
c
≤
z
∧
z
<
d
∧
z
<
b
37
36
bicomi
⊢
a
≤
z
∧
c
≤
z
∧
z
<
d
∧
z
<
b
↔
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
38
35
37
bitri
⊢
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
↔
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
39
38
bicomi
⊢
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
↔
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
40
39
anbi2i
⊢
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
41
34
40
bitri
⊢
z
∈
ℝ
∧
a
≤
z
∧
z
<
b
∧
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
42
30
41
bitrdi
⊢
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
z
∈
x
∩
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
43
18
19
42
syl2an
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
z
∈
x
∩
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
44
43
adantr
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
z
∈
x
∩
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
45
simpl
⊢
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
→
z
∈
ℝ
46
simprrl
⊢
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
→
c
≤
z
47
simprlr
⊢
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
→
z
<
d
48
45
46
47
jca32
⊢
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
→
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
49
44
48
syl6bi
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
z
∈
x
∩
y
→
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
50
3simpa
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
→
a
∈
ℝ
∧
b
∈
ℝ
51
3simpa
⊢
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
c
∈
ℝ
∧
d
∈
ℝ
52
50
51
anim12i
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
→
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
53
letr
⊢
a
∈
ℝ
∧
c
∈
ℝ
∧
z
∈
ℝ
→
a
≤
c
∧
c
≤
z
→
a
≤
z
54
53
3expia
⊢
a
∈
ℝ
∧
c
∈
ℝ
→
z
∈
ℝ
→
a
≤
c
∧
c
≤
z
→
a
≤
z
55
54
exp4a
⊢
a
∈
ℝ
∧
c
∈
ℝ
→
z
∈
ℝ
→
a
≤
c
→
c
≤
z
→
a
≤
z
56
55
ad2ant2r
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
→
z
∈
ℝ
→
a
≤
c
→
c
≤
z
→
a
≤
z
57
ltletr
⊢
z
∈
ℝ
∧
d
∈
ℝ
∧
b
∈
ℝ
→
z
<
d
∧
d
≤
b
→
z
<
b
58
57
3com13
⊢
b
∈
ℝ
∧
d
∈
ℝ
∧
z
∈
ℝ
→
z
<
d
∧
d
≤
b
→
z
<
b
59
58
expcomd
⊢
b
∈
ℝ
∧
d
∈
ℝ
∧
z
∈
ℝ
→
d
≤
b
→
z
<
d
→
z
<
b
60
59
3expia
⊢
b
∈
ℝ
∧
d
∈
ℝ
→
z
∈
ℝ
→
d
≤
b
→
z
<
d
→
z
<
b
61
60
ad2ant2l
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
→
z
∈
ℝ
→
d
≤
b
→
z
<
d
→
z
<
b
62
56
61
jcad
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
→
z
∈
ℝ
→
a
≤
c
→
c
≤
z
→
a
≤
z
∧
d
≤
b
→
z
<
d
→
z
<
b
63
anim12
⊢
a
≤
c
→
c
≤
z
→
a
≤
z
∧
d
≤
b
→
z
<
d
→
z
<
b
→
a
≤
c
∧
d
≤
b
→
c
≤
z
→
a
≤
z
∧
z
<
d
→
z
<
b
64
62
63
syl6
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
→
z
∈
ℝ
→
a
≤
c
∧
d
≤
b
→
c
≤
z
→
a
≤
z
∧
z
<
d
→
z
<
b
65
64
com23
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
→
a
≤
c
∧
d
≤
b
→
z
∈
ℝ
→
c
≤
z
→
a
≤
z
∧
z
<
d
→
z
<
b
66
anim12
⊢
c
≤
z
→
a
≤
z
∧
z
<
d
→
z
<
b
→
c
≤
z
∧
z
<
d
→
a
≤
z
∧
z
<
b
67
65
66
syl8
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
→
a
≤
c
∧
d
≤
b
→
z
∈
ℝ
→
c
≤
z
∧
z
<
d
→
a
≤
z
∧
z
<
b
68
67
imp31
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
a
≤
c
∧
d
≤
b
∧
z
∈
ℝ
→
c
≤
z
∧
z
<
d
→
a
≤
z
∧
z
<
b
69
68
ancrd
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
a
≤
c
∧
d
≤
b
∧
z
∈
ℝ
→
c
≤
z
∧
z
<
d
→
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
70
an42
⊢
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
↔
a
≤
z
∧
c
≤
z
∧
z
<
b
∧
z
<
d
71
an4
⊢
a
≤
z
∧
c
≤
z
∧
z
<
b
∧
z
<
d
↔
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
72
70
71
bitri
⊢
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
↔
a
≤
z
∧
z
<
b
∧
c
≤
z
∧
z
<
d
73
69
72
syl6ibr
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
a
≤
c
∧
d
≤
b
∧
z
∈
ℝ
→
c
≤
z
∧
z
<
d
→
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
74
simpr
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
a
≤
c
∧
d
≤
b
∧
z
∈
ℝ
→
z
∈
ℝ
75
73
74
jctild
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
a
≤
c
∧
d
≤
b
∧
z
∈
ℝ
→
c
≤
z
∧
z
<
d
→
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
76
52
75
sylanl1
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
∧
z
∈
ℝ
→
c
≤
z
∧
z
<
d
→
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
77
76
imp
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
∧
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
→
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
78
77
an32s
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
∧
c
≤
z
∧
z
<
d
∧
z
∈
ℝ
→
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
79
44
adantr
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
∧
c
≤
z
∧
z
<
d
→
z
∈
x
∩
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
80
79
adantr
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
∧
c
≤
z
∧
z
<
d
∧
z
∈
ℝ
→
z
∈
x
∩
y
↔
z
∈
ℝ
∧
a
≤
z
∧
z
<
d
∧
c
≤
z
∧
z
<
b
81
78
80
mpbird
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
∧
c
≤
z
∧
z
<
d
∧
z
∈
ℝ
→
z
∈
x
∩
y
82
81
expl
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
c
≤
z
∧
z
<
d
∧
z
∈
ℝ
→
z
∈
x
∩
y
83
82
ancomsd
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
→
z
∈
x
∩
y
84
49
83
impbid
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
z
∈
x
∩
y
↔
z
∈
ℝ
∧
c
≤
z
∧
z
<
d
85
84
27
bitr4di
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
z
∈
x
∩
y
↔
z
∈
z
∈
ℝ
|
c
≤
z
∧
z
<
d
86
16
17
11
85
eqrd
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
87
3
86
jca
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
d
∈
ℝ
∧
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
88
87
19.8ad
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
∃
d
d
∈
ℝ
∧
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
89
df-rex
⊢
∃
d
∈
ℝ
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
↔
∃
d
d
∈
ℝ
∧
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
90
88
89
sylibr
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
∃
d
∈
ℝ
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
91
2
90
jca
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
c
∈
ℝ
∧
∃
d
∈
ℝ
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
92
91
19.8ad
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
∃
c
c
∈
ℝ
∧
∃
d
∈
ℝ
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
93
df-rex
⊢
∃
c
∈
ℝ
∃
d
∈
ℝ
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
↔
∃
c
c
∈
ℝ
∧
∃
d
∈
ℝ
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
94
92
93
sylibr
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
∃
c
∈
ℝ
∃
d
∈
ℝ
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
95
1
icoreelrnab
⊢
x
∩
y
∈
I
↔
∃
c
∈
ℝ
∃
d
∈
ℝ
x
∩
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
96
94
95
sylibr
⊢
a
∈
ℝ
∧
b
∈
ℝ
∧
x
=
z
∈
ℝ
|
a
≤
z
∧
z
<
b
∧
c
∈
ℝ
∧
d
∈
ℝ
∧
y
=
z
∈
ℝ
|
c
≤
z
∧
z
<
d
∧
a
≤
c
∧
d
≤
b
→
x
∩
y
∈
I