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<b>let </b><font color="Maroon">F</font> be   <a href="funct_1.html#NM1">Function</a>;<br/><b>let </b><font color="Maroon">i</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">xi</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">Ai</font> be   <a href="subset_1.html#NM2">Subset</a> of <span class="p1">(<span class="default"><font color="Maroon">F</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">i</font></span>)</span>;<br/>







<b>assume </b><a NAME="E1:1"/><i><font color="Green">E20</font></i>: 
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="pralg_3.html#K3">proj</a> <font color="Maroon">F</font>,<font color="Maroon">i</font></span>)</span> <a href="relat_1.html#K10">"</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">xi</font></span><a href="tarski.html#K1">}</a></span></span>)</span> <a href="xboole_0.html#K3">/\</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="pralg_3.html#K3">proj</a> <font color="Maroon">F</font>,<font color="Maroon">i</font></span>)</span> <a href="relat_1.html#K10">"</a> <font color="Maroon">Ai</font></span>)</span> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="xboole_0.html#D7">XBOOLE_0:def 7</a><br/>

<b>consider </b><font color="Maroon">f</font> being    <a href="subset_1.html#M1">Element</a> of <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="pralg_3.html#K3">proj</a> <font color="Maroon">F</font>,<font color="Maroon">i</font></span>)</span> <a href="relat_1.html#K10">"</a> <span class="p2"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">xi</font></span><a href="tarski.html#K1">}</a></span></span>)</span> <a href="xboole_0.html#K3">/\</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="pralg_3.html#K3">proj</a> <font color="Maroon">F</font>,<font color="Maroon">i</font></span>)</span> <a href="relat_1.html#K10">"</a> <font color="Maroon">Ai</font></span>)</span>;<br/>
<a NAME="E3:1"/><i><font color="Green">E22</font></i>: 
( <font color="Maroon">f</font> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><a href="pralg_3.html#K3">proj</a> <font color="Maroon">F</font>,<font color="Maroon">i</font></span>)</span> <a href="relat_1.html#K10">"</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">xi</font></span><a href="tarski.html#K1">}</a></span> &amp; <font color="Maroon">f</font> <a href="hidden.html#R2">in</a> <span class="p1">(<span class="default"><a href="pralg_3.html#K3">proj</a> <font color="Maroon">F</font>,<font color="Maroon">i</font></span>)</span> <a href="relat_1.html#K10">"</a> <font color="Maroon">Ai</font> )
 
<b>by </b><i>, <a class="ref" href="xboole_0.html#D3">XBOOLE_0:def 3</a></i>;<br/>
<a NAME="E4:1"/><b>then </b>
<span class="p1">(<span class="default"><a href="pralg_3.html#K3">proj</a> <font color="Maroon">F</font>,<font color="Maroon">i</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">f</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K1">{</a><span class="default"><font color="Maroon">xi</font></span><a href="tarski.html#K1">}</a></span>
 
<b>by </b><i><a class="ref" href="funct_1.html#D13">FUNCT_1:def 13</a></i>;<br/>
<a NAME="E5:1"/><b>then </b>
<span class="p1">(<span class="default"><a href="pralg_3.html#K3">proj</a> <font color="Maroon">F</font>,<font color="Maroon">i</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">f</font> <a href="hidden.html#R1">=</a> <font color="Maroon">xi</font>
 
<b>by </b><i><a class="ref" href="tarski.html#D1">TARSKI:def 1</a></i>;<br/>
<b>hence </b><a NAME="E6:1"/>
<font color="Maroon">xi</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Ai</font>
 <b>by </b><i>, <a class="ref" href="funct_1.html#D13">FUNCT_1:def 13</a></i>;<br/>


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