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<b>let </b><font color="Maroon" title="c1">a</font>, <font color="Maroon" title="c2">b</font>, <font color="Maroon" title="c3">c</font>, <font color="Maroon" title="c4">d</font> be   <a href="struct_0.html#NM1" title="STRUCT_0:NM.1">Element</a> of <a href="midsp_1.html#K3" title="MIDSP_1:func.3">Example</a> ;<br/>

<b>thus </b><font color="Maroon" title="c1">a</font> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <font color="Maroon" title="c1">a</font> = 
 <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
<b>by </b><i><a class="ref" href="tarski.html#D1" title="TARSKI:def.1">TARSKI:def 1</a></i>
<br/>.= 
<font color="Maroon" title="c1">a</font>
<b>by </b><i><a class="ref" href="tarski.html#D1" title="TARSKI:def.1">TARSKI:def 1</a></i>
;<br/>

<b>thus </b><font color="Maroon" title="c1">a</font> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <font color="Maroon" title="c2">b</font> = 
 <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
<b>by </b><i><a class="ref" href="tarski.html#D1" title="TARSKI:def.1">TARSKI:def 1</a></i>
<br/>.= 
<font color="Maroon" title="c2">b</font> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <font color="Maroon" title="c1">a</font>
<b>by </b><i><a class="ref" href="tarski.html#D1" title="TARSKI:def.1">TARSKI:def 1</a></i>
;<br/>

<b>thus </b><span class="p1">(<span class="default"><font color="Maroon" title="c1">a</font> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <font color="Maroon" title="c2">b</font></span>)</span> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <span class="p1">(<span class="default"><font color="Maroon" title="c3">c</font> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <font color="Maroon" title="c4">d</font></span>)</span> = 
 <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
<b>by </b><i><a class="ref" href="tarski.html#D1" title="TARSKI:def.1">TARSKI:def 1</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon" title="c1">a</font> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <font color="Maroon" title="c3">c</font></span>)</span> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <span class="p1">(<span class="default"><font color="Maroon" title="c2">b</font> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <font color="Maroon" title="c4">d</font></span>)</span>
<b>by </b><i><a class="ref" href="tarski.html#D1" title="TARSKI:def.1">TARSKI:def 1</a></i>
;<br/>

<b>take </b><font color="Maroon" title="c5">x</font> = <font color="Maroon" title="c1">a</font>;<br/>

<b>thus </b><font color="Maroon" title="c5">x</font> <a href="midsp_1.html#K1" title="MIDSP_1:func.1">@</a> <font color="Maroon" title="c1">a</font> = 
 <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
<b>by </b><i><a class="ref" href="tarski.html#D1" title="TARSKI:def.1">TARSKI:def 1</a></i>
<br/>.= 
<font color="Maroon" title="c2">b</font>
<b>by </b><i><a class="ref" href="tarski.html#D1" title="TARSKI:def.1">TARSKI:def 1</a></i>
;<br/>


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