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<b>let </b><font color="Maroon">S</font> be  non <a href="struct_0.html#V3">empty</a> non <a href="msualg_1.html#V2">void</a>  <a href="msualg_1.html#L1">ManySortedSign</a> ;<br/><b>let </b><font color="Maroon">U0</font> be    <a href="msualg_1.html#L3">MSAlgebra</a> of <font color="Maroon">S</font>;<br/>



<b>reconsider </b><font color="Maroon">A</font> =  <a href="msualg_1.html#G3">MSAlgebra</a>(# the <a href="msualg_1.html#U4">Sorts</a> of <font color="Maroon">U0</font>,the <a href="msualg_1.html#U5">Charact</a> of <font color="Maroon">U0</font> #) as  <a href="msualg_1.html#V4">strict</a>  <a href="msualg_1.html#L3">MSAlgebra</a> of <font color="Maroon">S</font> ;<br/>
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="20_1"><b>now </b></a><div class="add"><b>thus </b><a NAME="E1:20_1"/>
the <a href="msualg_1.html#U4">Sorts</a> of <font color="Maroon">A</font> is   <a href="msualg_2.html#NM1">MSSubset</a> of <font color="Maroon">U0</font>
 <b>by </b><i><a class="ref" href="pboole.html#D23">PBOOLE:def 23</a></i>;<br/><b>let </b><font color="Maroon">B</font> be   <a href="msualg_2.html#NM1">MSSubset</a> of <font color="Maroon">U0</font>;<br/><b>assume </b><a NAME="E2:20_1"/><i><font color="Green">E20</font></i>: 
<font color="Maroon">B</font> <a href="pboole.html#R6">=</a> the <a href="msualg_1.html#U4">Sorts</a> of <font color="Maroon">A</font>
 ;<br/><b>hence </b><a NAME="E3:20_1"/>
<font color="Maroon">B</font> is <a href="msualg_2.html#V3" target="_self">opers_closed</a>
 <b>by </b><i/>;<br/><b>set </b><font color="Maroon">f1</font> = the <a href="msualg_1.html#U5">Charact</a> of <font color="Maroon">A</font>;<br/><b>set </b><font color="Maroon">f2</font> =  <a href="msualg_2.html#K4" target="_self">Opers</a> <font color="Maroon">U0</font>,<font color="Maroon">B</font>;<br/><a NAME="E4:20_1"/>
for <font color="Olive">x</font> being   <a href="hidden.html#M1">set</a>   st <font color="Olive">x</font> <a href="hidden.html#R2">in</a> the <a href="msualg_1.html#U1">OperSymbols</a> of <font color="Maroon">S</font> holds <br/>the <a href="msualg_1.html#U5">Charact</a> of <font color="Maroon">A</font> <a href="funct_1.html#K1">.</a> <font color="Olive">x</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="msualg_2.html#K4" target="_self">Opers</a> <font color="Maroon">U0</font>,<font color="Maroon">B</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Olive">x</font>
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="20_1_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/>

<b>assume </b><a NAME="E1:20_1_1"/>
<font color="Maroon">x</font> <a href="hidden.html#R2">in</a> the <a href="msualg_1.html#U1">OperSymbols</a> of <font color="Maroon">S</font>
 ;<br/>

<b>then reconsider </b><font color="Maroon">o1</font> = <font color="Maroon">x</font> as    <a href="subset_1.html#M1">Element</a> of the <a href="msualg_1.html#U1">OperSymbols</a> of <font color="Maroon">S</font> ;<br/>
<a NAME="E3:20_1_1"/>
( the <a href="msualg_1.html#U5">Charact</a> of <font color="Maroon">A</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">o1</font> <a href="hidden.html#R1">=</a>  <a href="msualg_1.html#K5">Den</a> <font color="Maroon">o1</font>,<font color="Maroon">U0</font> &amp; <span class="p1">(<span class="default"><a href="msualg_2.html#K4" target="_self">Opers</a> <font color="Maroon">U0</font>,<font color="Maroon">B</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">o1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">o1</font> <a href="msualg_2.html#K3" target="_self">/.</a> <font color="Maroon">B</font> )
 
<b>by </b><i>, <a class="ref" href="msualg_1.html#D11">MSUALG_1:def 11</a></i>;<br/>
<b>hence </b><a NAME="E4:20_1_1"/>
the <a href="msualg_1.html#U5">Charact</a> of <font color="Maroon">A</font> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="msualg_2.html#K4" target="_self">Opers</a> <font color="Maroon">U0</font>,<font color="Maroon">B</font></span>)</span> <a href="funct_1.html#K1">.</a> <font color="Maroon">x</font>
 <b>by </b><i>, </i>;<br/>


</div><b>end;</b></div><b>hence </b><a NAME="E5:20_1"/>
the <a href="msualg_1.html#U5">Charact</a> of <font color="Maroon">A</font> <a href="pboole.html#R6">=</a>  <a href="msualg_2.html#K4" target="_self">Opers</a> <font color="Maroon">U0</font>,<font color="Maroon">B</font>
 <b>by </b><i><a class="ref" href="pboole.html#T3">PBOOLE:3</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E3:20"/>
 <a href="msualg_1.html#G3">MSAlgebra</a>(# the <a href="msualg_1.html#U4">Sorts</a> of <font color="Maroon">U0</font>,the <a href="msualg_1.html#U5">Charact</a> of <font color="Maroon">U0</font> #) is    <a href="msualg_2.html#M1" target="_self">MSSubAlgebra</a> of <font color="Maroon">U0</font>
 <b>by </b><i/>;<br/>


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