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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>let </b><font color="Maroon">c<sub>2</sub></font> be   <a href="prob_1.html#NM3">SigmaField</a> of <font color="Maroon">c<sub>1</sub></font>;<br/><b>let </b><font color="Maroon">c<sub>3</sub></font> be    <a href="prob_1.html#M3">Probability</a> of <font color="Maroon">c<sub>2</sub></font>;<br/>





<a NAME="E1:35"/>
(  <a href="xboole_0.html#K1">{}</a>  <a href="tarski.html#R1">c=</a>  <a href="xboole_0.html#K1">{}</a>  &amp; <font color="Maroon">c<sub>3</sub></font> <a href="funct_1.html#K1">.</a> <a href="xboole_0.html#K1">{}</a>  <a href="hidden.html#R1">=</a> 0 &amp;  <a href="xboole_0.html#K1">{}</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">c<sub>2</sub></font> )
 
<b>by </b><i><a class="ref" href="prob_1.html#T64">PROB_1:64</a>, <a class="ref" href="prob_1.html#T42">PROB_1:42</a></i>;<br/>
<b>hence </b><a NAME="E2:35"/>
 <a href="xboole_0.html#K1">{}</a>  is    <a href="prob_4.html#M1" target="_self">thin</a> of <font color="Maroon">c<sub>3</sub></font>
 <b>by </b><i><a class="ref" href="prob_4.html#D4" target="_self">Def4</a></i>;<br/>


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