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<b>let </b><font color="Maroon">X</font> be  non <a href="struct_0.html#V3">empty</a> <a href="pre_topc.html#NM1">TopSpace</a>;<br/><b>let </b><font color="Maroon">Y</font> be  non <a href="struct_0.html#V3">empty</a> <a href="pre_topc.html#NM1">TopSpace</a>;<br/><b>let </b><font color="Maroon">X1</font> be  non <a href="struct_0.html#V3">empty</a>  <a href="pre_topc.html#M1">SubSpace</a> of <font color="Maroon">X</font>, <font color="Maroon">X2</font> be  non <a href="struct_0.html#V3">empty</a>  <a href="pre_topc.html#M1">SubSpace</a> of <font color="Maroon">X</font>;<br/><b>let </b><font color="Maroon">f1</font> be   <a href="struct_0.html#NM6">Function</a> of <font color="Maroon">X1</font>,<font color="Maroon">Y</font>;<br/><b>let </b><font color="Maroon">f2</font> be   <a href="struct_0.html#NM6">Function</a> of <font color="Maroon">X2</font>,<font color="Maroon">Y</font>;<br/>









<b>assume </b><a NAME="E1:150"/>
( <font color="Maroon">X1</font> <a href="tsep_1.html#R1">misses</a> <font color="Maroon">X2</font> or <font color="Maroon">f1</font> <a href="tmap_1.html#K3" target="_self">|</a> <span class="p1">(<span class="default"><font color="Maroon">X1</font> <a href="tsep_1.html#K2">meet</a> <font color="Maroon">X2</font></span>)</span> <a href="funct_2.html#R2">=</a> <font color="Maroon">f2</font> <a href="tmap_1.html#K3" target="_self">|</a> <span class="p1">(<span class="default"><font color="Maroon">X1</font> <a href="tsep_1.html#K2">meet</a> <font color="Maroon">X2</font></span>)</span> )
 ;<br/>

<a NAME="E2:150"/><b>then </b>
( <span class="p1">(<span class="default"><font color="Maroon">f1</font> <a href="tmap_1.html#K10" target="_self">union</a> <font color="Maroon">f2</font></span>)</span> <a href="tmap_1.html#K3" target="_self">|</a> <font color="Maroon">X1</font> <a href="funct_2.html#R2">=</a> <font color="Maroon">f1</font> &amp; <span class="p1">(<span class="default"><font color="Maroon">f1</font> <a href="tmap_1.html#K10" target="_self">union</a> <font color="Maroon">f2</font></span>)</span> <a href="tmap_1.html#K3" target="_self">|</a> <font color="Maroon">X2</font> <a href="funct_2.html#R2">=</a> <font color="Maroon">f2</font> )
 
<b>by </b><i><a class="ref" href="tmap_1.html#T27" target="_self">Th27</a></i>;<br/>
<b>hence </b><a NAME="E3:150"/>
<font color="Maroon">f1</font> <a href="tmap_1.html#K10" target="_self">union</a> <font color="Maroon">f2</font> <a href="funct_2.html#R1">=</a> <font color="Maroon">f2</font> <a href="tmap_1.html#K10" target="_self">union</a> <font color="Maroon">f1</font>
 <b>by </b><i><a class="ref" href="tmap_1.html#T29" target="_self">Th29</a></i>;<br/>


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