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<b>let </b><font color="Maroon">x1</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">x2</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">C</font> be   <a href="cat_1.html#NM4">Category</a>;<br/><b>let </b><font color="Maroon">p1</font> be   <a href="cat_1.html#NM2">Morphism</a> of <font color="Maroon">C</font>;<br/><b>let </b><font color="Maroon">p2</font> be   <a href="cat_1.html#NM2">Morphism</a> of <font color="Maroon">C</font>;<br/>









<b>set </b><font color="Maroon">F</font> = <font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">p1</font>,<font color="Maroon">p2</font>;<br/>
<b>set </b><font color="Maroon">F'</font> = <font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <span class="p1">(<span class="default"><font color="Maroon">p1</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span>,<span class="p1">(<span class="default"><font color="Maroon">p2</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span>;<br/>
<b>assume </b><a NAME="E1:16"/><i><font color="Green">E38</font></i>: 
<font color="Maroon">x1</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">x2</font>
 ;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="16_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>assume </b><a NAME="E1:16_1"/><i><font color="Green">E42</font></i>: 
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K2">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font></span><a href="tarski.html#K2">}</a></span>
 ;<br/><a NAME="E2:16_1"/><b>then </b>
( <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x1</font> or <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x2</font> )
 <b>by </b><i><a class="ref" href="tarski.html#D2">TARSKI:def 2</a></i>;<br/><a NAME="E3:16_1"/><b>then </b>
( ( <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">p1</font>,<font color="Maroon">p2</font></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">p1</font> &amp; <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <span class="p2">(<span class="default"><font color="Maroon">p1</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span>,<span class="p2">(<span class="default"><font color="Maroon">p2</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">p1</font> <a href="oppcat_1.html#K5">opp</a>  ) or ( <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">p1</font>,<font color="Maroon">p2</font></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">p2</font> &amp; <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <span class="p2">(<span class="default"><font color="Maroon">p1</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span>,<span class="p2">(<span class="default"><font color="Maroon">p2</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">p2</font> <a href="oppcat_1.html#K5">opp</a>  ) )
 <b>by </b><i>, </i>;<br/><b>hence </b><a NAME="E4:16_1"/>
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">p1</font>,<font color="Maroon">p2</font></span>)</span> <a href="cat_3.html#K5" target="_self">opp</a> </span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <span class="p2">(<span class="default"><font color="Maroon">p1</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span>,<span class="p2">(<span class="default"><font color="Maroon">p2</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">x</font>
 <b>by </b><i>, </i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E3:16"/>
<span class="p1">(<span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <font color="Maroon">p1</font>,<font color="Maroon">p2</font></span>)</span> <a href="cat_3.html#K5" target="_self">opp</a>  <a href="funct_2.html#R2">=</a> <font color="Maroon">x1</font>,<font color="Maroon">x2</font> <a href="funct_4.html#K5">--&gt;</a> <span class="p1">(<span class="default"><font color="Maroon">p1</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span>,<span class="p1">(<span class="default"><font color="Maroon">p2</font> <a href="oppcat_1.html#K5">opp</a> </span>)</span>
 <b>by </b><i/>;<br/>


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