<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">a</font> be    <a href="subset_1.html#M2">Element</a> of <font color="Maroon">o</font> <a href="cat_5.html#K13" target="_self">Hom</a> , <font color="Maroon">b</font> be    <a href="subset_1.html#M2">Element</a> of <font color="Maroon">o</font> <a href="cat_5.html#K13" target="_self">Hom</a> , <font color="Maroon">c</font> be    <a href="subset_1.html#M2">Element</a> of <font color="Maroon">o</font> <a href="cat_5.html#K13" target="_self">Hom</a> , <font color="Maroon">d</font> be    <a href="subset_1.html#M2">Element</a> of <font color="Maroon">o</font> <a href="cat_5.html#K13" target="_self">Hom</a> ;<br/><b>let </b><font color="Maroon">f</font> be   <a href="cat_1.html#NM2">Morphism</a> of <font color="Maroon">C</font>, <font color="Maroon">g</font> be   <a href="cat_1.html#NM2">Morphism</a> of <font color="Maroon">C</font>, <font color="Maroon">h</font> be   <a href="cat_1.html#NM2">Morphism</a> of <font color="Maroon">C</font>;<br/>



<b>assume </b><a NAME="E1:53_7"/>
(  <a href="cat_1.html#K2">dom</a> <font color="Maroon">f</font> <a href="hidden.html#R1">=</a>  <a href="cat_1.html#K3">cod</a> <font color="Maroon">a</font> &amp; <font color="Maroon">f</font> <a href="cat_1.html#K4">*</a> <font color="Maroon">a</font> <a href="hidden.html#R1">=</a> <font color="Maroon">b</font> &amp;  <a href="cat_1.html#K2">dom</a> <font color="Maroon">g</font> <a href="hidden.html#R1">=</a>  <a href="cat_1.html#K3">cod</a> <font color="Maroon">b</font> &amp; <font color="Maroon">g</font> <a href="cat_1.html#K4">*</a> <font color="Maroon">b</font> <a href="hidden.html#R1">=</a> <font color="Maroon">c</font> &amp;  <a href="cat_1.html#K2">dom</a> <font color="Maroon">h</font> <a href="hidden.html#R1">=</a>  <a href="cat_1.html#K3">cod</a> <font color="Maroon">c</font> &amp; <font color="Maroon">h</font> <a href="cat_1.html#K4">*</a> <font color="Maroon">c</font> <a href="hidden.html#R1">=</a> <font color="Maroon">d</font> )
 ;<br/>

<a NAME="E2:53_7"/><b>then </b>
(  <a href="cat_1.html#K2">dom</a> <font color="Maroon">g</font> <a href="hidden.html#R1">=</a>  <a href="cat_1.html#K3">cod</a> <font color="Maroon">f</font> &amp;  <a href="cat_1.html#K2">dom</a> <font color="Maroon">h</font> <a href="hidden.html#R1">=</a>  <a href="cat_1.html#K3">cod</a> <font color="Maroon">g</font> )
 
<b>by </b><i><a class="ref" href="cat_1.html#T42">CAT_1:42</a></i>;<br/>
<b>hence </b><a NAME="E3:53_7"/>
<font color="Maroon">H<sub>1</sub></font>(<font color="Maroon">h</font>,<font color="Maroon">H<sub>1</sub></font>(<font color="Maroon">g</font>,<font color="Maroon">f</font>)) <a href="hidden.html#R1">=</a> <font color="Maroon">H<sub>1</sub></font>(<font color="Maroon">H<sub>1</sub></font>(<font color="Maroon">h</font>,<font color="Maroon">g</font>),<font color="Maroon">f</font>)
 <b>by </b><i><a class="ref" href="cat_1.html#T43">CAT_1:43</a></i>;<br/>


</div>
