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<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">G</font> be   <a href="group_1.html#NM1">Group</a>;<br/><b>let </b><font color="Maroon">N1</font> be  <a href="group_1.html#V1">strict</a> <a href="group_3.html#V1">normal</a>  <a href="group_2.html#M1">Subgroup</a> of <font color="Maroon">G</font>, <font color="Maroon">N2</font> be  <a href="group_1.html#V1">strict</a> <a href="group_3.html#V1">normal</a>  <a href="group_2.html#M1">Subgroup</a> of <font color="Maroon">G</font>;<br/>





<a NAME="E1:8"/>
<font color="Maroon">N1</font> <a href="group_4.html#K7">*</a> <font color="Maroon">N2</font> <a href="hidden.html#R1">=</a> <font color="Maroon">N2</font> <a href="group_4.html#K7">*</a> <font color="Maroon">N1</font>
 
<b>by </b><i><a class="ref" href="group_4.html#T64">GROUP_4:64</a></i>;<br/>
<b>hence </b><a NAME="E2:8"/>
( <font color="Maroon">x</font> <a href="rlvect_1.html#R1">in</a> <font color="Maroon">N1</font> <a href="group_4.html#K8">"\/"</a> <font color="Maroon">N2</font> iff  ex <font color="Olive">a</font>, <font color="Olive">b</font> being  <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">G</font> st <br/>( <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Olive">a</font> <a href="group_1.html#K1">*</a> <font color="Olive">b</font> &amp; <font color="Olive">a</font> <a href="rlvect_1.html#R1">in</a> <font color="Maroon">N1</font> &amp; <font color="Olive">b</font> <a href="rlvect_1.html#R1">in</a> <font color="Maroon">N2</font> ) )
 <b>by </b><i/>;<br/>


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