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<b>assume </b><a NAME="E1:24_1_1"/>
<font color="Maroon">c<sub>2</sub></font> <a href="subset_1.html#K3">`</a>  is <a href="xboole_0.html#V1">empty</a>
 ;<br/>

<b>then </b><span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="subset_1.html#K3">`</a> </span>)</span> <a href="subset_1.html#K3">`</a>  = 
<span class="p1">(<span class="default"><a href="subset_1.html#K1">{}</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="subset_1.html#K3">`</a> 

<br/>.= 
 <a href="subset_1.html#K2">[#]</a> <font color="Maroon">c<sub>1</sub></font>

<br/>.= 
<font color="Maroon">c<sub>1</sub></font>

;<br/>
<b>hence </b><a NAME="E3:24_1_1"/>
contradiction
 <b>by </b><i><a class="ref" href="tex_2.html#T5" target="_self">Th5</a></i>;<br/>


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