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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/>

<b>consider </b><font color="Maroon">c<sub>2</sub></font> being    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>
<a NAME="E2:9"/>
<span class="p1"><a href="domain_1.html#K6">{</a><span class="default"><font color="Maroon">c<sub>2</sub></font></span><a href="domain_1.html#K6">}</a></span> is   <a href="rpr_1.html#NM1">El_ev</a> of <font color="Maroon">c<sub>1</sub></font>
 
<b>by </b><i><a class="ref" href="rpr_1.html#T7" target="_self">Th7</a></i>;<br/>
<b>hence </b><a NAME="E3:9"/>
ex <font color="Olive">b<sub>1</sub></font> being  <a href="rpr_1.html#NM1">El_ev</a> of <font color="Maroon">c<sub>1</sub></font> st <font color="Olive">b<sub>1</sub></font> is   <a href="rpr_1.html#NM1">El_ev</a> of <font color="Maroon">c<sub>1</sub></font>
 ;<br/>


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