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

<b>let </b><font color="Maroon">c<sub>1</sub></font>, <font color="Maroon">c<sub>2</sub></font>, <font color="Maroon">c<sub>3</sub></font> be   <a href="group_1.html#NM1">Group</a>;<br/>





<b>assume </b><b>that </b><br/><a NAME="E1:90"/><i><font color="Green">E67</font></i>: 
<font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font> <a href="group_6.html#R1" target="_self">are_isomorphic</a> 
 <b>and </b><br/><a NAME="E2:90"/><i><font color="Green">E68</font></i>: 
<font color="Maroon">c<sub>2</sub></font>,<font color="Maroon">c<sub>3</sub></font> <a href="group_6.html#R1" target="_self">are_isomorphic</a> 
 ;<br/>

<b>consider </b><font color="Maroon">c<sub>4</sub></font> being   <a href="group_6.html#NM2">Homomorphism</a> of <font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font><b> such that </b><br/><a NAME="E4:90"/><i><font color="Green">E69</font></i>: 
<font color="Maroon">c<sub>4</sub></font> <a href="group_6.html#NR3" target="_self">is_isomorphism</a> 
 <b>by </b><i><a class="txt" href="group_6.html#E1:90"><i><font color="Green">E67</font></i></a>, <a class="ref" href="group_6.html#D15" target="_self">Def15</a></i>;<br/>
<b>consider </b><font color="Maroon">c<sub>5</sub></font> being   <a href="group_6.html#NM2">Homomorphism</a> of <font color="Maroon">c<sub>2</sub></font>,<font color="Maroon">c<sub>3</sub></font><b> such that </b><br/><a NAME="E6:90"/><i><font color="Green">E70</font></i>: 
<font color="Maroon">c<sub>5</sub></font> <a href="group_6.html#NR3" target="_self">is_isomorphism</a> 
 <b>by </b><i><a class="txt" href="group_6.html#E2:90"><i><font color="Green">E68</font></i></a>, <a class="ref" href="group_6.html#D15" target="_self">Def15</a></i>;<br/>
<a NAME="E7:90"/>
<font color="Maroon">c<sub>5</sub></font> <a href="group_6.html#K8" target="_self">*</a> <font color="Maroon">c<sub>4</sub></font> <a href="group_6.html#NR3" target="_self">is_isomorphism</a> 
 
<b>by </b><i><a class="txt" href="group_6.html#E4:90"><i><font color="Green">E69</font></i></a>, <a class="txt" href="group_6.html#E6:90"><i><font color="Green">E70</font></i></a>, <a class="ref" href="group_6.html#T74" target="_self">Th74</a></i>;<br/>
<b>hence </b><a NAME="E8:90"/>
<font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>3</sub></font> <a href="group_6.html#R1" target="_self">are_isomorphic</a> 
 <b>by </b><i><a class="ref" href="group_6.html#D15" target="_self">Def15</a></i>;<br/>


</div>
