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<b>let </b><font color="Maroon">P</font> be   <a href="relat_1.html#NM1">Relation</a>;<br/><b>let </b><font color="Maroon">R</font> be   <a href="relat_1.html#NM1">Relation</a>;<br/>



<b>assume </b><a NAME="E1:31"/>
<font color="Maroon">P</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">R</font>
 ;<br/>

<a NAME="E2:31"/><b>then </b>
(  <a href="relat_1.html#K1" target="_self">dom</a> <font color="Maroon">P</font> <a href="tarski.html#R1">c=</a>  <a href="relat_1.html#K1" target="_self">dom</a> <font color="Maroon">R</font> &amp;  <a href="relat_1.html#K2" target="_self">rng</a> <font color="Maroon">P</font> <a href="tarski.html#R1">c=</a>  <a href="relat_1.html#K2" target="_self">rng</a> <font color="Maroon">R</font> )
 
<b>by </b><i/>;<br/>
<a NAME="E3:31"/><b>then </b>
<span class="p1">(<span class="default"><a href="relat_1.html#K1" target="_self">dom</a> <font color="Maroon">P</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><a href="relat_1.html#K2" target="_self">rng</a> <font color="Maroon">P</font></span>)</span> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><a href="relat_1.html#K1" target="_self">dom</a> <font color="Maroon">R</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><a href="relat_1.html#K2" target="_self">rng</a> <font color="Maroon">R</font></span>)</span>
 
<b>by </b><i><a class="ref" href="xboole_1.html#T13">XBOOLE_1:13</a></i>;<br/>
<a NAME="E4:31"/><b>then </b>
 <a href="relat_1.html#K3" target="_self">field</a> <font color="Maroon">P</font> <a href="tarski.html#R1">c=</a> <span class="p1">(<span class="default"><a href="relat_1.html#K1" target="_self">dom</a> <font color="Maroon">R</font></span>)</span> <a href="xboole_0.html#K2">\/</a> <span class="p1">(<span class="default"><a href="relat_1.html#K2" target="_self">rng</a> <font color="Maroon">R</font></span>)</span>
 
;<br/>
<b>hence </b><a NAME="E5:31"/>
 <a href="relat_1.html#K3" target="_self">field</a> <font color="Maroon">P</font> <a href="tarski.html#R1">c=</a>  <a href="relat_1.html#K3" target="_self">field</a> <font color="Maroon">R</font>
 ;<br/>


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