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<b>let </b><font color="Maroon">A</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">o</font> be   <a href="binop_1.html#NM2">BinOp</a> of <font color="Maroon">A</font>;<br/><b>let </b><font color="Maroon">e1</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font>;<br/><b>let </b><font color="Maroon">e2</font> be    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">A</font>;<br/>







<b>assume </b><b>that </b><br/><a NAME="E1:20"/><i><font color="Green">E27</font></i>: 
<font color="Maroon">e1</font> <a href="binop_1.html#R1" target="_self">is_a_left_unity_wrt</a> <font color="Maroon">o</font>
 <b>and </b><br/><a NAME="E2:20"/><i><font color="Green">E28</font></i>: 
<font color="Maroon">e2</font> <a href="binop_1.html#R2" target="_self">is_a_right_unity_wrt</a> <font color="Maroon">o</font>
 ;<br/>

<b>thus </b><font color="Maroon">e1</font> = 
<font color="Maroon">o</font> <a href="binop_1.html#K1" target="_self">.</a> <font color="Maroon">e1</font>,<font color="Maroon">e2</font>
<b>by </b><i>, </i>
<br/>.= 
<font color="Maroon">e2</font>
<b>by </b><i>, </i>
;<br/>


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