Metamath Proof Explorer


Theorem cldregopn

Description: A set if regularly open iff it is the interior of some closed set. (Contributed by Jeff Hankins, 27-Sep-2009)

Ref Expression
Hypothesis opnregcld.1 X=J
Assertion cldregopn JTopAXintJclsJA=AcClsdJA=intJc

Proof

Step Hyp Ref Expression
1 opnregcld.1 X=J
2 1 clscld JTopAXclsJAClsdJ
3 eqcom intJclsJA=AA=intJclsJA
4 3 biimpi intJclsJA=AA=intJclsJA
5 fveq2 c=clsJAintJc=intJclsJA
6 5 rspceeqv clsJAClsdJA=intJclsJAcClsdJA=intJc
7 2 4 6 syl2an JTopAXintJclsJA=AcClsdJA=intJc
8 7 ex JTopAXintJclsJA=AcClsdJA=intJc
9 cldrcl cClsdJJTop
10 1 cldss cClsdJcX
11 1 ntrss2 JTopcXintJcc
12 9 10 11 syl2anc cClsdJintJcc
13 1 clsss2 cClsdJintJccclsJintJcc
14 12 13 mpdan cClsdJclsJintJcc
15 1 ntrss JTopcXclsJintJccintJclsJintJcintJc
16 9 10 14 15 syl3anc cClsdJintJclsJintJcintJc
17 1 ntridm JTopcXintJintJc=intJc
18 9 10 17 syl2anc cClsdJintJintJc=intJc
19 1 ntrss3 JTopcXintJcX
20 9 10 19 syl2anc cClsdJintJcX
21 1 clsss3 JTopintJcXclsJintJcX
22 9 20 21 syl2anc cClsdJclsJintJcX
23 1 sscls JTopintJcXintJcclsJintJc
24 9 20 23 syl2anc cClsdJintJcclsJintJc
25 1 ntrss JTopclsJintJcXintJcclsJintJcintJintJcintJclsJintJc
26 9 22 24 25 syl3anc cClsdJintJintJcintJclsJintJc
27 18 26 eqsstrrd cClsdJintJcintJclsJintJc
28 16 27 eqssd cClsdJintJclsJintJc=intJc
29 28 adantl JTopAXcClsdJintJclsJintJc=intJc
30 2fveq3 A=intJcintJclsJA=intJclsJintJc
31 id A=intJcA=intJc
32 30 31 eqeq12d A=intJcintJclsJA=AintJclsJintJc=intJc
33 29 32 syl5ibrcom JTopAXcClsdJA=intJcintJclsJA=A
34 33 rexlimdva JTopAXcClsdJA=intJcintJclsJA=A
35 8 34 impbid JTopAXintJclsJA=AcClsdJA=intJc