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<div class="add">

<b>defpred </b><font color="Maroon">S<sub>1</sub></font>[   <a href="hidden.html#M1">set</a> ] <b>means </b>for <font color="Olive">t</font> being   <a href="hidden.html#M1">set</a>   st <font color="Olive">t</font> <a href="hidden.html#R1">=</a> <font color="Maroon">a<sub>1</sub></font> holds <br/>( <font color="Olive">t</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp; <font color="Olive">t</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> &amp; <font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Olive">t</font> is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font> );<br/>
<b>consider </b><font color="Maroon">D</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E2:42_1_1"/><i><font color="Green">E24</font></i>: 
for <font color="Olive">t</font> being   <a href="hidden.html#M1">set</a>  holds <br/> ( <font color="Olive">t</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font> iff ( <font color="Olive">t</font> <a href="hidden.html#R2">in</a>  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">Omega</font> &amp; <font color="Maroon">S<sub>1</sub></font>[<font color="Olive">t</font>] ) )
 <b>from </b><i><a class="ref" href="xboole_0.html#S1">XBOOLE_0:sch 1</a>();<br/></i>
<a NAME="E3:42_1_1"/><i><font color="Green">E36</font></i>: 
for <font color="Olive">B</font> being   <a href="hidden.html#M1">set</a>  holds <br/> ( <font color="Olive">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font> iff ( <font color="Olive">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp; <font color="Olive">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> &amp; <font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Olive">B</font> is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font> ) )
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="42_1_1_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">B</font> be    <a href="hidden.html#M1">set</a> ;<br/>

<a NAME="E1:42_1_1_1"/>
( <font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp; <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> &amp; <font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">B</font> is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font> implies <font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font> )
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="42_1_1_1_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:42_1_1_1_1"/><i><font color="Green">E39</font></i>: 
( <font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp; <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> &amp; <font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">B</font> is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font> )
 ;<br/>

<a NAME="E2:42_1_1_1_1"/><b>then </b>
for <font color="Olive">t</font> being   <a href="hidden.html#M1">set</a>   st <font color="Olive">t</font> <a href="hidden.html#R1">=</a> <font color="Maroon">B</font> holds <br/>( <font color="Olive">t</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp; <font color="Olive">t</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> &amp; <font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Olive">t</font> is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font> )
 
;<br/>
<b>hence </b><a NAME="E3:42_1_1_1_1"/>
<font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font>
 <b>by </b><i>, </i>;<br/>


</div><b>end;</b></div>
<b>hence </b><a NAME="E2:42_1_1_1"/>
( <font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font> iff ( <font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp; <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> &amp; <font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">B</font> is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font> ) )
 <b>by </b><i/>;<br/>


</div><b>end;</b></div>
<a NAME="E4:42_1_1"/>
<font color="Maroon">D</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="42_1_1_2"><b>proof </b></a><div class="add">

<b>consider </b><font color="Maroon">B</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E2:42_1_1_2"/><i><font color="Green">E48</font></i>: 
( <font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp;  ex <font color="Olive">C</font> being   <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font> st <font color="Maroon">A</font> <a href="hidden.html#R1">=</a> <font color="Maroon">B</font> <a href="xboole_0.html#K2">\/</a> <font color="Olive">C</font> )
 <b>by </b><i/>;<br/>
<b>consider </b><font color="Maroon">C</font> being    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font><b> such that </b><br/><a NAME="E4:42_1_1_2"/><i><font color="Green">E49</font></i>: 
<font color="Maroon">A</font> <a href="hidden.html#R1">=</a> <font color="Maroon">B</font> <a href="xboole_0.html#K2">\/</a> <font color="Maroon">C</font>
 <b>by </b><i/>;<br/>
<b>consider </b><font color="Maroon">E</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E6:42_1_1_2"/><i><font color="Green">E50</font></i>: 
( <font color="Maroon">E</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp; <font color="Maroon">C</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">E</font> &amp; <font color="Maroon">P</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">E</font> <a href="hidden.html#R1">=</a> 0 )
 <b>by </b><i><a class="txt" href="prob_4.html#E2:42_1_1"><i><font color="Green">E24</font></i></a></i>;<br/>
<a NAME="E7:42_1_1_2"/>
<font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">B</font> <a href="hidden.html#R1">=</a> <font color="Maroon">C</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">B</font>
 
<b>by </b><i><a class="ref" href="prob_4.html#T1" target="_self">Th1</a>, <a class="ref" href="xboole_1.html#T40">XBOOLE_1:40</a></i>;<br/>
<a NAME="E8:42_1_1_2"/><b>then </b>
<font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">C</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T36">XBOOLE_1:36</a></i>;<br/>
<a NAME="E9:42_1_1_2"/><b>then </b><i><font color="Green">E51</font></i>: 
<font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">E</font>
 
<b>by </b><i><a class="txt" href="prob_4.html#E3:42_1_1"><i><font color="Green">E36</font></i></a>, <a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/>
<a NAME="E10:42_1_1_2"/><i><font color="Green">E52</font></i>: 
<font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Maroon">B</font> is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font>
 
<b>by </b><i><a class="txt" href="prob_4.html#E3:42_1_1"><i><font color="Green">E36</font></i></a>, <a class="ref" href="prob_4.html#T2" target="_self">Th2</a>, <a class="txt" href="prob_4.html#E2:42_1_1"><i><font color="Green">E24</font></i></a></i>;<br/>
<a NAME="E11:42_1_1_2"/>
<font color="Maroon">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font>
 
<b>by </b><i><a class="ref" href="prob_4.html#T1" target="_self">Th1</a>, <a class="ref" href="xboole_1.html#T7">XBOOLE_1:7</a></i>;<br/>
<b>hence </b><a NAME="E12:42_1_1_2"/>
<font color="Maroon">D</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 <b>by </b><i>, , </i>;<br/>


</div><b>end;</b></div>
<b>then consider </b><font color="Maroon">x</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E6:42_1_1"/><i><font color="Green">E54</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font>
 <b>by </b><i><a class="ref" href="xboole_0.html#D1">XBOOLE_0:def 1</a></i>;<br/>
<a NAME="E7:42_1_1"/>
<font color="Maroon">D</font> <a href="tarski.html#R1">c=</a>  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">Omega</font>
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="42_1_1_3"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">B</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:42_1_1_3"/>
<font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font>
 ;<br/>

<a NAME="E2:42_1_1_3"/><b>then </b>
<font color="Maroon">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font>
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:42_1_1_3"/>
<font color="Maroon">B</font> <a href="hidden.html#R2">in</a>  <a href="zfmisc_1.html#K1">bool</a> <font color="Maroon">Omega</font>
 ;<br/>


</div><b>end;</b></div>
<b>then reconsider </b><font color="Maroon">D</font> = <font color="Maroon">D</font> as  non <a href="xboole_0.html#V1">empty</a> <a href="setfam_1.html#NM1">Subset-Family</a> of <font color="Maroon">Omega</font> <b>by </b><i/>;<br/>
<b>take </b>
<font color="Maroon">D</font>
;<br/>

<b>thus </b><a NAME="E9:42_1_1"/>
for <font color="Olive">B</font> being   <a href="hidden.html#M1">set</a>  holds <br/> ( <font color="Olive">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">D</font> iff ( <font color="Olive">B</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Sigma</font> &amp; <font color="Olive">B</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font> &amp; <font color="Maroon">A</font> <a href="subset_1.html#K7">\</a> <font color="Olive">B</font> is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">P</font> ) )
 <b>by </b><i/>;<br/>


</div>
