<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon">X1</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">X2</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">f1</font> be   <a href="funct_2.html#NM1">Function</a> of <font color="Maroon">X1</font>,<font color="Maroon">Y1</font>;<br/><b>let </b><font color="Maroon">f2</font> be   <a href="funct_2.html#NM1">Function</a> of <font color="Maroon">X2</font>,<font color="Maroon">Y2</font>;<br/>











<b>assume </b><a NAME="E1:91"/>
( ( <font color="Maroon">Y1</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  implies <font color="Maroon">X1</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  ) &amp; ( <font color="Maroon">Y2</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  implies <font color="Maroon">X2</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  ) )
 ;<br/>

<a NAME="E2:91"/><b>then </b>
(  <a href="relset_1.html#K4">dom</a> <font color="Maroon">f1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">X1</font> &amp;  <a href="relset_1.html#K4">dom</a> <font color="Maroon">f2</font> <a href="hidden.html#R1">=</a> <font color="Maroon">X2</font> )
 
<b>by </b><i><a class="ref" href="funct_2.html#D1">FUNCT_2:def 1</a></i>;<br/>
<b>hence </b><a NAME="E3:91"/>
<span class="p1"><a href="funct_3.html#K16" target="_self">[:</a><span class="default"><font color="Maroon">f1</font>,<font color="Maroon">f2</font></span><a href="funct_3.html#K16" target="_self">:]</a></span> <a href="hidden.html#R1">=</a> <span class="p1"><a href="funct_3.html#K13" target="_self">&lt;:</a><span class="default"><span class="p2">(<span class="default"><font color="Maroon">f1</font> <a href="funct_1.html#NK3" target="_self">*</a> <span class="p3">(<span class="default"><a href="funct_3.html#K9" target="_self">pr1</a> <font color="Maroon">X1</font>,<font color="Maroon">X2</font></span>)</span></span>)</span>,<span class="p2">(<span class="default"><font color="Maroon">f2</font> <a href="funct_1.html#NK3" target="_self">*</a> <span class="p3">(<span class="default"><a href="funct_3.html#K10" target="_self">pr2</a> <font color="Maroon">X1</font>,<font color="Maroon">X2</font></span>)</span></span>)</span></span><a href="funct_3.html#K13" target="_self">:&gt;</a></span>
 <b>by </b><i/>;<br/>


</div>
