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<b>let </b><font color="Maroon">V</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">C</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">A</font> be    <a href="subset_1.html#M2">Element</a> of  <a href="substlat.html#K1">SubstitutionSet</a> <font color="Maroon">V</font>,<font color="Maroon">C</font>;<br/><b>let </b><font color="Maroon">B</font> be    <a href="subset_1.html#M2">Element</a> of  <a href="substlat.html#K1">SubstitutionSet</a> <font color="Maroon">V</font>,<font color="Maroon">C</font>;<br/>







<b>assume </b><a NAME="E1:11"/><i><font color="Green">E21</font></i>: 
 <a href="substlat.html#K3">mi</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="substlat.html#K4">^</a> <font color="Maroon">B</font></span>)</span> <a href="hidden.html#R1">=</a> <font color="Maroon">A</font>
 ;<br/>

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

<a NAME="E2:11"/><i><font color="Green">E24</font></i>: 
 <a href="substlat.html#K3">mi</a> <span class="p1">(<span class="default"><font color="Maroon">A</font> <a href="substlat.html#K4">^</a> <font color="Maroon">B</font></span>)</span> <a href="heyting1.html#R1">c=</a> <font color="Maroon">A</font> <a href="substlat.html#K4">^</a> <font color="Maroon">B</font>
 
<b>by </b><i><a class="ref" href="substlat.html#T8">SUBSTLAT:8</a></i>;<br/>
<b>assume </b><a NAME="E3:11"/>
<font color="Maroon">a</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font>
 ;<br/>

<b>then consider </b><font color="Maroon">b</font> being    <a href="hidden.html#M1">set</a> , <font color="Maroon">c</font> being    <a href="hidden.html#M1">set</a> <b> such that </b><br/><a NAME="E5:11"/><i><font color="Green">E25</font></i>: 
( <font color="Maroon">b</font> <a href="hidden.html#R2">in</a> <font color="Maroon">A</font> &amp; <font color="Maroon">c</font> <a href="hidden.html#R2">in</a> <font color="Maroon">B</font> &amp; <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>, , <a class="ref" href="substlat.html#T15">SUBSTLAT:15</a></i>;<br/>
<b>take </b>
<font color="Maroon">c</font>
;<br/>

<b>thus </b><a NAME="E6:11"/>
( <font color="Maroon">c</font> <a href="hidden.html#R2">in</a> <font color="Maroon">B</font> &amp; <font color="Maroon">c</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">a</font> )
 <b>by </b><i>, <a class="ref" href="xboole_1.html#T7">XBOOLE_1:7</a></i>;<br/>


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