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<b>let </b><font color="Maroon" title="c20">a</font> be    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Maroon" title="c4">A</font>;<br/>

<a NAME="E1:23"/>
( <font color="Maroon" title="c20">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c1">x</font> or <font color="Maroon" title="c20">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c2">y</font> )
 
<b>by </b><i><a class="ref" href="tarski.html#D2" title="TARSKI:def.2">TARSKI:def 2</a></i>;<br/>
<b>hence </b><a NAME="E2:23"/>
( <font color="Maroon" title="c18">od0</font> <a href="binop_1.html#K2" title="BINOP_1:func.2">.</a> <font color="Maroon" title="c20">a</font>,<font color="Maroon" title="c5">nd</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c20">a</font> &amp; <font color="Maroon" title="c18">od0</font> <a href="binop_1.html#K2" title="BINOP_1:func.2">.</a> <font color="Maroon" title="c5">nd</font>,<font color="Maroon" title="c20">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c20">a</font> )
 <b>by </b><i><a class="txt" href="realset2.html#E25"><i><font color="Green" title="E16">Lm11</font></i></a>, <a class="txt" href="realset2.html#E26"><i><font color="Green" title="E17">Lm12</font></i></a>, <a class="txt" href="realset2.html#E28"><i><font color="Green" title="E19">Lm14</font></i></a>, <a class="txt" href="realset2.html#E29"><i><font color="Green" title="E20">Lm15</font></i></a>, <a class="txt" href="realset2.html#E31"><i><font color="Green" title="E22">Lm17</font></i></a>, <a class="txt" href="realset2.html#E32"><i><font color="Green" title="E23">Lm18</font></i></a>, <a class="ref" href="funct_1.html#D4" title="FUNCT_1:def.4">FUNCT_1:def 4</a></i>;<br/>


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