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<b>let </b><font color="Maroon">X1</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">X2</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>let </b><font color="Maroon">f</font> be   <a href="funct_1.html#NM1">Function</a>;<br/>









<b>assume </b><a NAME="E1:62"/>
( <font color="Maroon">X1</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">X2</font> &amp; <font color="Maroon">Y1</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">Y2</font> )
 ;<br/>

<a NAME="E2:62"/><b>then </b>
( <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X1</font>,<font color="Maroon">Y1</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X2</font>,<font color="Maroon">Y1</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> &amp; <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X2</font>,<font color="Maroon">Y1</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X2</font>,<font color="Maroon">Y2</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> )
 
<b>by </b><i><a class="ref" href="partfun1.html#T1" target="_self">Th1</a>, </i>;<br/>
<b>hence </b><a NAME="E3:62"/>
<span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X1</font>,<font color="Maroon">Y1</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span> <a href="tarski.html#R1">c=</a> <span class="p1"><a href="partfun1.html#K3" target="_self">&lt;:</a><span class="default"><font color="Maroon">f</font>,<font color="Maroon">X2</font>,<font color="Maroon">Y2</font></span><a href="partfun1.html#K3" target="_self">:&gt;</a></span>
 <b>by </b><i><a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/>


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