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<b>let </b><font color="Maroon">I</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">sf</font> be   <a href="setfam_1.html#NM1">Subset-Family</a> of <font color="Maroon">I</font>;<br/>



<b>assume </b><a NAME="E1:3"/>
<font color="Maroon">sf</font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<a NAME="E2:3"/><b>then </b>
 <a href="setfam_1.html#K8">Intersect</a> <font color="Maroon">sf</font> <a href="hidden.html#R1">=</a>  <a href="setfam_1.html#K6">meet</a> <font color="Maroon">sf</font>
 
<b>by </b><i><a class="ref" href="setfam_1.html#D10">SETFAM_1:def 10</a></i>;<br/>
<b>hence </b><a NAME="E3:3"/>
 <a href="setfam_1.html#K8">Intersect</a> <font color="Maroon">sf</font> <a href="tarski.html#R1">c=</a>  <a href="setfam_1.html#K5">union</a> <font color="Maroon">sf</font>
 <b>by </b><i><a class="ref" href="setfam_1.html#T3">SETFAM_1:3</a></i>;<br/>


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