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<b>let </b><font color="Maroon">x</font> be   <a href="zf_lang.html#NM1">Variable</a>;<br/><b>let </b><font color="Maroon">M</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/>



<b>consider </b><font color="Maroon">v</font> being   <a href="funct_2.html#NM1">Function</a> of  <a href="zf_lang.html#K1">VAR</a> ,<font color="Maroon">M</font>;<br/>
<a NAME="E2:76"/>
not <font color="Maroon">M</font>,<font color="Maroon">v</font> <a href="zf_model.html#R1">|=</a> <font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">x</font>
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:76"/>
not <font color="Maroon">M</font> <a href="zf_model.html#R2">|=</a> <font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">x</font>
 <b>by </b><i><a class="ref" href="zf_model.html#D5">ZF_MODEL:def 5</a></i>;<br/>

<b>let </b><font color="Maroon">v</font> be   <a href="funct_2.html#NM1">Function</a> of  <a href="zf_lang.html#K1">VAR</a> ,<font color="Maroon">M</font>; <i><font color="Red">:: according to </font></i><a class="ref" href="zf_model.html#D5">ZF_MODEL:def 5</a><br/>

<a NAME="E4:76"/>
not <font color="Maroon">M</font>,<font color="Maroon">v</font> <a href="zf_model.html#R1">|=</a> <font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">x</font>
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E5:76"/>
<font color="Maroon">M</font>,<font color="Maroon">v</font> <a href="zf_model.html#R1">|=</a>  <a href="zf_lang.html#K6">'not'</a> <span class="p1">(<span class="default"><font color="Maroon">x</font> <a href="zf_lang.html#K5">'in'</a> <font color="Maroon">x</font></span>)</span>
 <b>by </b><i><a class="ref" href="zf_model.html#T14">ZF_MODEL:14</a></i>;<br/>


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