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<b>let </b><font color="Maroon">c<sub>1</sub></font> be  non <a href="struct_0.html#V3">empty</a>  <a href="fin_topo.html#L1">FT_Space_Str</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be   <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>



<a NAME="E1:41"/><i><font color="Green">E28</font></i>: 
( ( for <font color="Olive">b<sub>1</sub></font> being  <a href="nat_1.html#NM1">Nat</a><br/>for <font color="Olive">b<sub>2</sub></font> being  <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">c<sub>1</sub></font> st <font color="Olive">b<sub>2</sub></font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="fintopo3.html#K8" target="_self">Fdfl</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_2.html#K3">.</a> <font color="Olive">b<sub>1</sub></font> holds <br/><span class="p1">(<span class="default"><a href="fintopo3.html#K8" target="_self">Fdfl</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_2.html#K3">.</a> <span class="p1">(<span class="default"><font color="Olive">b<sub>1</sub></font> <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="hidden.html#R1">=</a> <font color="Olive">b<sub>2</sub></font> <a href="fintopo3.html#K1" target="_self">^d</a>  ) &amp; <span class="p1">(<span class="default"><a href="fintopo3.html#K8" target="_self">Fdfl</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_2.html#K3">.</a> 0 <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>2</sub></font> )
 
<b>by </b><i><a class="ref" href="fintopo3.html#D8" target="_self">Def8</a></i>;<br/>
<a NAME="E2:41"/>
for <font color="Olive">b<sub>1</sub></font> being  <a href="struct_0.html#NM2">Subset</a> of <font color="Maroon">c<sub>1</sub></font> st <font color="Olive">b<sub>1</sub></font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="fintopo3.html#K8" target="_self">Fdfl</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_2.html#K3">.</a> 0 holds <br/><span class="p1">(<span class="default"><a href="fintopo3.html#K8" target="_self">Fdfl</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_2.html#K3">.</a> <span class="p1">(<span class="default">0 <a href="nat_1.html#K1">+</a> 1</span>)</span> <a href="hidden.html#R1">=</a> <font color="Olive">b<sub>1</sub></font> <a href="fintopo3.html#K1" target="_self">^d</a> 
 
<b>by </b><i><a class="ref" href="fintopo3.html#D8" target="_self">Def8</a></i>;<br/>
<a NAME="E3:41"/><b>then </b>
<span class="p1">(<span class="default"><a href="fintopo3.html#K8" target="_self">Fdfl</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="funct_2.html#K3">.</a> 1 <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>2</sub></font> <a href="fintopo3.html#K1" target="_self">^d</a> 
 
<b>by </b><i><a class="txt" href="fintopo3.html#E1:41"><i><font color="Green">E28</font></i></a></i>;<br/>
<b>hence </b><a NAME="E4:41"/>
 <a href="fintopo3.html#K9" target="_self">Fdfl</a> <font color="Maroon">c<sub>2</sub></font>,1 <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>2</sub></font> <a href="fintopo3.html#K1" target="_self">^d</a> 
 ;<br/>


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