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<b>let </b><font color="Maroon">c<sub>1</sub></font>, <font color="Maroon">c<sub>2</sub></font> be  non <a href="struct_0.html#V3">empty</a>  <a href="robbins1.html#L1">ComplStr</a> ;<br/><b>let </b><font color="Maroon">c<sub>3</sub></font> be   <a href="struct_0.html#NM1">Element</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="struct_0.html#NM1">Element</a> of <font color="Maroon">c<sub>2</sub></font>;<br/>





<b>assume </b><a NAME="E1:46"/><i><font color="Green">E21</font></i>: 
( the <a href="robbins1.html#U1">Compl</a> of <font color="Maroon">c<sub>1</sub></font> <a href="funct_2.html#R1">=</a> the <a href="robbins1.html#U1">Compl</a> of <font color="Maroon">c<sub>2</sub></font> &amp; <font color="Maroon">c<sub>3</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> )
 ;<br/>

<font color="Maroon">c<sub>3</sub></font> <a href="robbins1.html#K3">`</a>  = 
the <a href="robbins1.html#U1">Compl</a> of <font color="Maroon">c<sub>2</sub></font> <a href="funct_2.html#K3">.</a> <font color="Maroon">c<sub>4</sub></font>
<b>by </b><i><a class="txt" href="robbins3.html#E1:46"><i><font color="Green">E21</font></i></a>, <a class="ref" href="robbins1.html#D3">ROBBINS1:def 3</a></i>
<br/>.= 
<font color="Maroon">c<sub>4</sub></font> <a href="robbins1.html#K3">`</a> 
<b>by </b><i><a class="ref" href="robbins1.html#D3">ROBBINS1:def 3</a></i>
;<br/>
<b>hence </b><a NAME="E3:46"/>
<font color="Maroon">c<sub>3</sub></font> <a href="robbins1.html#K3">`</a>  <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> <a href="robbins1.html#K3">`</a> 
 ;<br/>


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