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<a NAME="E1:19_1"/><i><font color="Green">E20</font></i>: 
<font color="Maroon">F<sub>2</sub></font>() <a href="hidden.html#R1">=</a> <span class="p1">{<span class="default"> <span class="p2"><a href="tarski.html#K4">[</a><span class="default"><font color="Olive">o</font>,<font color="Maroon">F<sub>4</sub></font>(<font color="Olive">o</font>)</span><a href="tarski.html#K4">]</a></span> where <font color="Olive">o</font> is    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">F<sub>1</sub></font>() : <font color="Maroon">P<sub>1</sub></font>[<font color="Olive">o</font>] </span>}</span> 
 
<b>by </b><i/>;<br/>
<a NAME="E2:19_1"/>
 <a href="relat_1.html#K1">dom</a> <font color="Maroon">F<sub>2</sub></font>() <a href="hidden.html#R1">=</a> <span class="p1">{<span class="default"> <font color="Olive">o</font> where <font color="Olive">o</font> is    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">F<sub>1</sub></font>() : <font color="Maroon">P<sub>1</sub></font>[<font color="Olive">o</font>] </span>}</span> 
 
<b>from </b><i><a class="ref" href="altcat_2.html#S2" target="_self">ALTCAT_2:sch 2</a>();<br/></i>
<a NAME="E3:19_1"/><b>then </b><i><font color="Green">E21</font></i>: 
<font color="Maroon">F<sub>3</sub></font>() <a href="hidden.html#R2">in</a>  <a href="relat_1.html#K1">dom</a> <font color="Maroon">F<sub>2</sub></font>()
 
<b>by </b><i/>;<br/>
<a NAME="E4:19_1"/>
<span class="p1"><a href="tarski.html#K4">[</a><span class="default"><font color="Maroon">F<sub>3</sub></font>(),<font color="Maroon">F<sub>4</sub></font>(<font color="Maroon">F<sub>3</sub></font>())</span><a href="tarski.html#K4">]</a></span> <a href="hidden.html#R2">in</a> <span class="p1">{<span class="default"> <span class="p2"><a href="tarski.html#K4">[</a><span class="default"><font color="Olive">o</font>,<font color="Maroon">F<sub>4</sub></font>(<font color="Olive">o</font>)</span><a href="tarski.html#K4">]</a></span> where <font color="Olive">o</font> is    <a href="subset_1.html#M1">Element</a> of <font color="Maroon">F<sub>1</sub></font>() : <font color="Maroon">P<sub>1</sub></font>[<font color="Olive">o</font>] </span>}</span> 
 
<b>by </b><i/>;<br/>
<b>hence </b><a NAME="E5:19_1"/>
<font color="Maroon">F<sub>2</sub></font>() <a href="funct_1.html#K1">.</a> <font color="Maroon">F<sub>3</sub></font>() <a href="hidden.html#R1">=</a> <font color="Maroon">F<sub>4</sub></font>(<font color="Maroon">F<sub>3</sub></font>())
 <b>by </b><i>, , <a class="ref" href="funct_1.html#D4">FUNCT_1:def 4</a></i>;<br/>


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