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<b>let </b><font color="Maroon">A</font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">B</font> be  non <a href="xboole_0.html#V1">empty</a> <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">A</font>, <font color="Maroon">C</font> be  non <a href="xboole_0.html#V1">empty</a> <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">A</font>;<br/><b>let </b><font color="Maroon">D</font> be  non <a href="xboole_0.html#V1">empty</a> <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">B</font>;<br/>





<b>assume </b><a NAME="E1:5"/><i><font color="Green">E29</font></i>: 
<font color="Maroon">C</font> <a href="hidden.html#R1">=</a> <font color="Maroon">D</font>
 ;<br/>

<span class="p1">(<span class="default"><a href="funct_3.html#K6">incl</a> <font color="Maroon">B</font></span>)</span> <a href="partfun1.html#K1">*</a> <span class="p1">(<span class="default"><a href="funct_3.html#K6">incl</a> <font color="Maroon">D</font></span>)</span> = 
 <a href="partfun1.html#K6">id</a> <span class="p1">(<span class="default"><font color="Maroon">B</font> <a href="subset_1.html#K9">/\</a> <font color="Maroon">D</font></span>)</span>
<b>by </b><i><a class="ref" href="funct_1.html#T43">FUNCT_1:43</a></i>
<br/>.= 
 <a href="funct_3.html#K6">incl</a> <font color="Maroon">C</font>
<b>by </b><i>, <a class="ref" href="xboole_1.html#T28">XBOOLE_1:28</a></i>
;<br/>
<b>hence </b><a NAME="E3:5"/>
 <a href="funct_3.html#K6">incl</a> <font color="Maroon">C</font> <a href="funct_2.html#R1">=</a> <span class="p1">(<span class="default"><a href="funct_3.html#K6">incl</a> <font color="Maroon">B</font></span>)</span> <a href="partfun1.html#K1">*</a> <span class="p1">(<span class="default"><a href="funct_3.html#K6">incl</a> <font color="Maroon">D</font></span>)</span>
 ;<br/>


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