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<b>let </b><font color="Maroon">c<sub>1</sub></font>, <font color="Maroon">c<sub>2</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">c<sub>3</sub></font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">c<sub>1</sub></font>;<br/><b>let </b><font color="Maroon">c<sub>4</sub></font> be   <a href="subset_1.html#NM2">Subset</a> of <font color="Maroon">c<sub>2</sub></font>;<br/>







<b>assume </b><a NAME="E1:7"/><i><font color="Green">E7</font></i>: 
<span class="p1"><a href="mcart_1.html#K12">[:</a><span class="default"><font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span><a href="mcart_1.html#K12">:]</a></span> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="xboole_0.html#K1">{}</a> 
 ;<br/>

<b>thus </b><span class="p1">(<span class="default"><a href="funct_3.html#K1">.:</a> <span class="p2">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font></span>)</span></span>)</span> <a href="funct_1.html#K1">.</a> <span class="p1"><a href="mcart_1.html#K12">[:</a><span class="default"><font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span><a href="mcart_1.html#K12">:]</a></span> = 
<span class="p1">(<span class="default"><a href="funct_3.html#K9">pr1</a> <font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="relset_1.html#K10">.:</a> <span class="p1"><a href="mcart_1.html#K12">[:</a><span class="default"><font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span><a href="mcart_1.html#K12">:]</a></span>
<b>by </b><i><a class="ref" href="borsuk_1.html#T9" target="_self">Th9</a></i>
<br/>.= 
<font color="Maroon">c<sub>3</sub></font>
<b>by </b><i><a class="txt" href="borsuk_1.html#E1:7"><i><font color="Green">E7</font></i></a>, <a class="ref" href="borsuk_1.html#T12" target="_self">Th12</a></i>
;<br/>

<b>thus </b><span class="p1">(<span class="default"><a href="funct_3.html#K1">.:</a> <span class="p2">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font></span>)</span></span>)</span> <a href="funct_1.html#K1">.</a> <span class="p1"><a href="mcart_1.html#K12">[:</a><span class="default"><font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span><a href="mcart_1.html#K12">:]</a></span> = 
<span class="p1">(<span class="default"><a href="funct_3.html#K10">pr2</a> <font color="Maroon">c<sub>1</sub></font>,<font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="relset_1.html#K10">.:</a> <span class="p1"><a href="mcart_1.html#K12">[:</a><span class="default"><font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span><a href="mcart_1.html#K12">:]</a></span>
<b>by </b><i><a class="ref" href="borsuk_1.html#T10" target="_self">Th10</a></i>
<br/>.= 
<font color="Maroon">c<sub>4</sub></font>
<b>by </b><i><a class="txt" href="borsuk_1.html#E1:7"><i><font color="Green">E7</font></i></a>, <a class="ref" href="borsuk_1.html#T12" target="_self">Th12</a></i>
;<br/>


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