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<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be   <a href="cat_1.html#NM4">Category</a>;<br/><b>let </b><font color="Maroon">c<sub>3</sub></font> be   <a href="cat_1.html#NM2">Morphism</a> of <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="oppcat_1.html#K2">opp</a> </span>)</span>;<br/>





<b>set </b><font color="Maroon">c<sub>4</sub></font> = <font color="Maroon">c<sub>1</sub></font> <a href="cat_3.html#K1" target="_self">--&gt;</a> <font color="Maroon">c<sub>3</sub></font>;<br/>
<b>set </b><font color="Maroon">c<sub>5</sub></font> = <font color="Maroon">c<sub>1</sub></font> <a href="cat_3.html#K1" target="_self">--&gt;</a> <span class="p1">(<span class="default"><a href="oppcat_1.html#K6">opp</a> <font color="Maroon">c<sub>3</sub></font></span>)</span>;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="19_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">c<sub>6</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/><b>assume </b><a NAME="E1:19_1"/><i><font color="Green">E13</font></i>: 
<font color="Maroon">c<sub>6</sub></font> <a href="hidden.html#R2">in</a> <font color="Maroon">c<sub>1</sub></font>
 ;<br/><a NAME="E2:19_1"/><b>then </b>
( <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="cat_3.html#K1" target="_self">--&gt;</a> <font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">c<sub>6</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>3</sub></font> &amp; <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="cat_3.html#K1" target="_self">--&gt;</a> <span class="p2">(<span class="default"><a href="oppcat_1.html#K6">opp</a> <font color="Maroon">c<sub>3</sub></font></span>)</span></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">c<sub>6</sub></font> <a href="hidden.html#R1">=</a>  <a href="oppcat_1.html#K6">opp</a> <font color="Maroon">c<sub>3</sub></font> )
 <b>by </b><i><a class="ref" href="cat_3.html#T2" target="_self">Th2</a></i>;<br/><b>hence </b><a NAME="E3:19_1"/>
<span class="p1">(<span class="default"><a href="cat_3.html#K6" target="_self">opp</a> <span class="p2">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="cat_3.html#K1" target="_self">--&gt;</a> <font color="Maroon">c<sub>3</sub></font></span>)</span></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">c<sub>6</sub></font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="cat_3.html#K1" target="_self">--&gt;</a> <span class="p2">(<span class="default"><a href="oppcat_1.html#K6">opp</a> <font color="Maroon">c<sub>3</sub></font></span>)</span></span>)</span> <a href="finseq_4.html#K4">/.</a> <font color="Maroon">c<sub>6</sub></font>
 <b>by </b><i><a class="txt" href="cat_3.html#E1:19_1"><i><font color="Green">E13</font></i></a>, <a class="ref" href="cat_3.html#D6" target="_self">Def6</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E2:19"/>
 <a href="cat_3.html#K6" target="_self">opp</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="cat_3.html#K1" target="_self">--&gt;</a> <font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="funct_2.html#R2">=</a> <font color="Maroon">c<sub>1</sub></font> <a href="cat_3.html#K1" target="_self">--&gt;</a> <span class="p1">(<span class="default"><a href="oppcat_1.html#K6">opp</a> <font color="Maroon">c<sub>3</sub></font></span>)</span>
 <b>by </b><i><a class="ref" href="cat_3.html#T1" target="_self">Th1</a></i>;<br/>


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