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<b>let </b><font color="Maroon">Y</font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">X</font>;<br/><b>let </b><font color="Maroon">x</font> be  <a href="facirc_1.html#V1">pair</a>  <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="facirc_1.html#D2">FACIRC_1:def 2</a><br/>



<b>assume </b><a NAME="E1:102_2_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <font color="Maroon">Y</font>
 ;<br/>

<b>hence </b><a NAME="E2:102_2_1"/>
contradiction
 <b>by </b><i><a class="ref" href="facirc_1.html#D2">FACIRC_1:def 2</a></i>;<br/>


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