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<b>let </b><font color="Maroon">A</font> be   <a href="cat_1.html#NM4">Category</a>;<br/><b>let </b><font color="Maroon">B</font> be   <a href="cat_1.html#NM4">Category</a>;<br/><b>let </b><font color="Maroon">F1</font> be    <a href="cat_1.html#M2">Functor</a> of <font color="Maroon">A</font>,<font color="Maroon">B</font>;<br/><b>let </b><font color="Maroon">F2</font> be    <a href="cat_1.html#M2">Functor</a> of <font color="Maroon">A</font>,<font color="Maroon">B</font>;<br/><b>let </b><font color="Maroon">s</font> be    <a href="nattra_1.html#M2">natural_transformation</a> of <font color="Maroon">F1</font>,<font color="Maroon">F2</font>;<br/>









<b>assume </b><a NAME="E1:44"/><i><font color="Green">E18</font></i>: 
<font color="Maroon">F1</font> <a href="nattra_1.html#R2">is_naturally_transformable_to</a> <font color="Maroon">F2</font>
 ;<br/>

<a NAME="E2:44"/><i><font color="Green">E19</font></i>: 
( <span class="p1">(<span class="default"><a href="cat_1.html#K15">id</a> <font color="Maroon">B</font></span>)</span> <a href="cat_1.html#K14">*</a> <font color="Maroon">F1</font> <a href="funct_2.html#R2">=</a> <font color="Maroon">F1</font> &amp; <span class="p1">(<span class="default"><a href="cat_1.html#K15">id</a> <font color="Maroon">B</font></span>)</span> <a href="cat_1.html#K14">*</a> <font color="Maroon">F2</font> <a href="funct_2.html#R2">=</a> <font color="Maroon">F2</font> )
 
<b>by </b><i/>;<br/>
<b>then reconsider </b><font color="Maroon">t</font> = <span class="p1">(<span class="default"><a href="cat_1.html#K15">id</a> <font color="Maroon">B</font></span>)</span> <a href="isocat_1.html#K4" target="_self">*</a> <font color="Maroon">s</font> as    <a href="nattra_1.html#M2">natural_transformation</a> of <font color="Maroon">F1</font>,<font color="Maroon">F2</font> ;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="44_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">a</font> be   <a href="cat_1.html#NM1">Object</a> of <font color="Maroon">A</font>;<br/><a NAME="E1:44_1"/><i><font color="Green">E22</font></i>: 
 <a href="cat_1.html#K6">Hom</a> <span class="p1">(<span class="default"><font color="Maroon">F1</font> <a href="cat_1.html#K13">.</a> <font color="Maroon">a</font></span>)</span>,<span class="p1">(<span class="default"><font color="Maroon">F2</font> <a href="cat_1.html#K13">.</a> <font color="Maroon">a</font></span>)</span> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 <b>by </b><i>, </i>;<br/><b>thus </b><font color="Maroon">t</font> <a href="nattra_1.html#K5">.</a> <font color="Maroon">a</font> = 
<span class="p1">(<span class="default"><a href="cat_1.html#K15">id</a> <font color="Maroon">B</font></span>)</span> <a href="nattra_1.html#K3">.</a> <span class="p1">(<span class="default"><font color="Maroon">s</font> <a href="nattra_1.html#K5">.</a> <font color="Maroon">a</font></span>)</span>
<b>by </b><i>, , <a class="txt" href="isocat_1.html#E1:44_1"><i><font color="Green">E22</font></i></a></i>
<br/>.= 
<span class="p1">(<span class="default"><a href="cat_1.html#K15">id</a> <font color="Maroon">B</font></span>)</span> <a href="funct_2.html#K3">.</a> <span class="p1">(<span class="default"><font color="Maroon">s</font> <a href="nattra_1.html#K5">.</a> <font color="Maroon">a</font></span>)</span>
<b>by </b><i>, <a class="ref" href="nattra_1.html#D1">NATTRA_1:def 1</a></i>
<br/>.= 
<font color="Maroon">s</font> <a href="nattra_1.html#K5">.</a> <font color="Maroon">a</font>
<b>by </b><i><a class="ref" href="funct_1.html#T35">FUNCT_1:35</a></i>
;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E5:44"/>
<span class="p1">(<span class="default"><a href="cat_1.html#K15">id</a> <font color="Maroon">B</font></span>)</span> <a href="isocat_1.html#K4" target="_self">*</a> <font color="Maroon">s</font> <a href="funct_2.html#R2">=</a> <font color="Maroon">s</font>
 <b>by </b><i>, </i>;<br/>


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