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<b>consider </b><font color="Maroon">c<sub>2</sub></font> being  non <a href="tex_2.html#V1" target="_self">proper</a> <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>
<b>reconsider </b><font color="Maroon">c<sub>3</sub></font> = <font color="Maroon">c<sub>2</sub></font> as  non <a href="xboole_0.html#V1">empty</a> <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">c<sub>1</sub></font> ;<br/>
<b>take </b>
<font color="Maroon">c<sub>3</sub></font>
;<br/>

<b>thus </b><a NAME="E3:17_2_1"/>
( not <font color="Maroon">c<sub>3</sub></font> is <a href="realset1.html#V1">trivial</a> &amp; not <font color="Maroon">c<sub>3</sub></font> is <a href="tex_2.html#V1" target="_self">proper</a> )
 ;<br/>


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