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<b>let </b><font color="Maroon">z</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">X</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">y1</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">y2</font> be    <a href="hidden.html#M1">set</a> ;<br/>







<b>assume </b><a NAME="E1:16"/>
<font color="Maroon">z</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="zfmisc_1.html#K2">[:</a><span class="default"><font color="Maroon">X</font>,<span class="p2"><a href="tarski.html#K2">{</a><span class="default"><font color="Maroon">y1</font>,<font color="Maroon">y2</font></span><a href="tarski.html#K2">}</a></span></span><a href="zfmisc_1.html#K2">:]</a></span>
 ;<br/>

<a NAME="E2:16"/><b>then </b>
( <font color="Maroon">z</font> <a href="mcart_1.html#K1" target="_self">`1</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">X</font> &amp; <font color="Maroon">z</font> <a href="mcart_1.html#K2" target="_self">`2</a>  <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K2">{</a><span class="default"><font color="Maroon">y1</font>,<font color="Maroon">y2</font></span><a href="tarski.html#K2">}</a></span> )
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E3:16"/>
( <font color="Maroon">z</font> <a href="mcart_1.html#K1" target="_self">`1</a>  <a href="hidden.html#R2">in</a> <font color="Maroon">X</font> &amp; ( <font color="Maroon">z</font> <a href="mcart_1.html#K2" target="_self">`2</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">y1</font> or <font color="Maroon">z</font> <a href="mcart_1.html#K2" target="_self">`2</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">y2</font> ) )
 <b>by </b><i><a class="ref" href="tarski.html#D2">TARSKI:def 2</a></i>;<br/>


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