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<b>let </b><font color="Maroon" title="c1">f</font>, <font color="Maroon" title="c2">g</font> be  <a href="grcat_1.html#V2" title="GRCAT_1:attr.2">strict</a> <a href="grcat_1.html#NM1" title="GRCAT_1:NM.1">GroupMorphism</a>;<br/>

<b>assume </b><a NAME="E1:49"/>
 <a href="grcat_1.html#K9" title="GRCAT_1:func.9">dom</a> <font color="Maroon" title="c2">g</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="grcat_1.html#K10" title="GRCAT_1:func.10">cod</a> <font color="Maroon" title="c1">f</font>
 ;<br/>

<b>then consider </b><font color="Maroon" title="c3">G1</font>, <font color="Maroon" title="c4">G2</font>, <font color="Maroon" title="c5">G3</font> being   <a href="mod_1.html#NM1" title="MOD_1:NM.1">AddGroup</a>, <font color="Maroon" title="c6">f0</font> being   <a href="struct_0.html#NM6" title="STRUCT_0:NM.6">Function</a> of <font color="Maroon" title="c3">G1</font>,<font color="Maroon" title="c4">G2</font>, <font color="Maroon" title="c7">g0</font> being   <a href="struct_0.html#NM6" title="STRUCT_0:NM.6">Function</a> of <font color="Maroon" title="c4">G2</font>,<font color="Maroon" title="c5">G3</font><b> such that </b><br/><a NAME="E3:49"/><i><font color="Green" title="E30">A1</font></i>: 
( <font color="Maroon" title="c1">f</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="grcat_1.html#G1" title="GRCAT_1:aggr.1">GroupMorphismStr</a>(# <font color="Maroon" title="c3">G1</font>,<font color="Maroon" title="c4">G2</font>,<font color="Maroon" title="c6">f0</font> #) &amp; <font color="Maroon" title="c2">g</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="grcat_1.html#G1" title="GRCAT_1:aggr.1">GroupMorphismStr</a>(# <font color="Maroon" title="c4">G2</font>,<font color="Maroon" title="c5">G3</font>,<font color="Maroon" title="c7">g0</font> #) &amp; <font color="Maroon" title="c2">g</font> <a href="grcat_1.html#K15" title="GRCAT_1:func.15">*</a> <font color="Maroon" title="c1">f</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="grcat_1.html#G1" title="GRCAT_1:aggr.1">GroupMorphismStr</a>(# <font color="Maroon" title="c3">G1</font>,<font color="Maroon" title="c5">G3</font>,<span class="p1">(<span class="default"><font color="Maroon" title="c7">g0</font> <a href="partfun1.html#K1" title="PARTFUN1:func.1">*</a> <font color="Maroon" title="c6">f0</font></span>)</span> #) )
 <b>by </b><i><a class="ref" href="grcat_1.html#T30" target="_self" title="GRCAT_1:th.30">Th30</a></i>;<br/>
<b>thus </b><a NAME="E4:49"/>
 <a href="grcat_1.html#K9" title="GRCAT_1:func.9">dom</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">g</font> <a href="grcat_1.html#K15" title="GRCAT_1:func.15">*</a> <font color="Maroon" title="c1">f</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="grcat_1.html#K9" title="GRCAT_1:func.9">dom</a> <font color="Maroon" title="c1">f</font>
 <b>by </b><i><a class="txt" href="grcat_1.html#E3:49"><i><font color="Green" title="E30">A1</font></i></a></i>;<br/>

<b>thus </b><a NAME="E5:49"/>
 <a href="grcat_1.html#K10" title="GRCAT_1:func.10">cod</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">g</font> <a href="grcat_1.html#K15" title="GRCAT_1:func.15">*</a> <font color="Maroon" title="c1">f</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="grcat_1.html#K10" title="GRCAT_1:func.10">cod</a> <font color="Maroon" title="c2">g</font>
 <b>by </b><i><a class="txt" href="grcat_1.html#E3:49"><i><font color="Green" title="E30">A1</font></i></a></i>;<br/>


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