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<b>let </b><font color="Maroon">c<sub>1</sub></font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/>

<a NAME="E1:135"/>
 <a href="group_1.html#G1">HGrStr</a>(# <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="finseq_2.html#K3">*</a> </span>)</span>,<span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="monoid_0.html#K12" target="_self">-concatenation</a> </span>)</span> #) <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>1</sub></font> <a href="monoid_0.html#K10" target="_self">*+^</a> 
 
<b>by </b><i><a class="ref" href="monoid_0.html#T68" target="_self">Th68</a></i>;<br/>
<b>hence </b><a NAME="E2:135"/>
( <font color="Maroon">c<sub>1</sub></font> <a href="monoid_0.html#K12" target="_self">-concatenation</a>  <a href="setwiseo.html#NR1" target="_self">has_a_unity</a>  &amp;  <a href="binop_1.html#K3">the_unity_wrt</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>1</sub></font> <a href="monoid_0.html#K12" target="_self">-concatenation</a> </span>)</span> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">c<sub>1</sub></font> <a href="monoid_0.html#K12" target="_self">-concatenation</a>  is <a href="binop_1.html#V2">associative</a> )
 <b>by </b><i><a class="ref" href="monoid_0.html#D10" target="_self">Def10</a>, <a class="ref" href="monoid_0.html#D12" target="_self">Def12</a>, <a class="ref" href="monoid_0.html#T69" target="_self">Th69</a></i>;<br/>


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