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<b>let </b><font color="Maroon">A</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">B</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">R</font> be    <a href="relset_1.html#M2">Relation</a> of <font color="Maroon">A</font>,<font color="Maroon">B</font>;<br/>





<i><font color="Green">E21</font></i>: <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">R</font> <a href="relset_1.html#K6">~</a> </span>)</span> <a href="relset_2.html#K6" target="_self">*</a> <font color="Maroon">R</font></span>)</span> <a href="relset_1.html#K10">.:</a> <font color="Maroon">B</font> = 
<font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">R</font> <a href="relset_1.html#K6">~</a> </span>)</span> <a href="relset_1.html#K10">.:</a> <font color="Maroon">B</font></span>)</span>
<b>by </b><i><a class="ref" href="relat_1.html#T159">RELAT_1:159</a></i>
<br/>.= 
<font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <span class="p1">(<span class="default"><a href="funct_5.html#K1">proj1</a> <font color="Maroon">R</font></span>)</span>
<b>by </b><i><a class="ref" href="relset_2.html#T3" target="_self">Th3</a></i>
;<br/>
<b>thus </b><a NAME="E2:66"/>
<font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <font color="Maroon">A</font> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">R</font> <a href="relset_1.html#K6">~</a> </span>)</span> <a href="relset_2.html#K6" target="_self">*</a> <font color="Maroon">R</font></span>)</span> <a href="relset_1.html#K10">.:</a> <font color="Maroon">B</font>
  <i><font color="Red">:: according to </font></i><a class="ref" href="xboole_0.html#D10">XBOOLE_0:def 10</a><div><a class="txt" onclick="hs2(this)" href="javascript:()" title="66_2"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">x</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="E1:66_2"/><i><font color="Green">E22</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <font color="Maroon">A</font>
 ;<br/>

<a NAME="E2:66_2"/><i><font color="Green">E23</font></i>: 
<font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <font color="Maroon">A</font> <a href="hidden.html#R1">=</a> <font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="xboole_0.html#K3">/\</a> <span class="p2">(<span class="default"><a href="funct_5.html#K1">proj1</a> <font color="Maroon">R</font></span>)</span></span>)</span>
 
<b>by </b><i><a class="txt" href="relset_2.html#E3:66"><i><font color="Green">E25</font></i></a></i>;<br/>
<a NAME="E3:66_2"/>
<font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="xboole_0.html#K3">/\</a> <span class="p2">(<span class="default"><a href="funct_5.html#K1">proj1</a> <font color="Maroon">R</font></span>)</span></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <font color="Maroon">A</font></span>)</span> <a href="subset_1.html#K9">/\</a> <span class="p1">(<span class="default"><font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <span class="p2">(<span class="default"><a href="funct_5.html#K1">proj1</a> <font color="Maroon">R</font></span>)</span></span>)</span>
 
<b>by </b><i><a class="ref" href="relat_1.html#T154">RELAT_1:154</a></i>;<br/>
<b>hence </b><a NAME="E4:66_2"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">R</font> <a href="relset_1.html#K6">~</a> </span>)</span> <a href="relset_2.html#K6" target="_self">*</a> <font color="Maroon">R</font></span>)</span> <a href="relset_1.html#K10">.:</a> <font color="Maroon">B</font>
 <b>by </b><i>, , <a class="ref" href="relset_2.html#T4" target="_self">Th4</a>, <a class="ref" href="xboole_0.html#D3">XBOOLE_0:def 3</a></i>;<br/>


</div><b>end;</b></div>

<b>let </b><font color="Maroon">x</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="E3:66"/><i><font color="Green">E25</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">R</font> <a href="relset_1.html#K6">~</a> </span>)</span> <a href="relset_2.html#K6" target="_self">*</a> <font color="Maroon">R</font></span>)</span> <a href="relset_1.html#K10">.:</a> <font color="Maroon">B</font>
 ;<br/>

<a NAME="E4:66"/>
 <a href="funct_5.html#K1">proj1</a> <font color="Maroon">R</font> <a href="tarski.html#R1">c=</a>  <a href="relset_1.html#K4">dom</a> <font color="Maroon">R</font>
 
<b>by </b><i><a class="ref" href="funct_5.html#T21">FUNCT_5:21</a></i>;<br/>
<a NAME="E5:66"/><b>then </b>
 <a href="funct_5.html#K1">proj1</a> <font color="Maroon">R</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">A</font>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/>
<a NAME="E6:66"/><b>then </b>
<font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <span class="p1">(<span class="default"><a href="funct_5.html#K1">proj1</a> <font color="Maroon">R</font></span>)</span> <a href="tarski.html#R1">c=</a> <font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <font color="Maroon">A</font>
 
<b>by </b><i><a class="ref" href="relat_1.html#T156">RELAT_1:156</a></i>;<br/>
<b>hence </b><a NAME="E7:66"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">R</font> <a href="relset_1.html#K10">.:</a> <font color="Maroon">A</font>
 <b>by </b><i>, <a class="ref" href="relset_2.html#T4" target="_self">Th4</a></i>;<br/>


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