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<b>let </b><font color="Maroon">S</font> be   <a href="catalg_1.html#NM1">Signature</a>, <font color="Maroon">T</font> be   <a href="catalg_1.html#NM1">Signature</a>;<br/>

<b>assume </b><a NAME="E1:59"/><i><font color="Green">E25</font></i>: 
the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">S</font> is <a href="xboole_0.html#V1">empty</a>
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="struct_0.html#D1">STRUCT_0:def 1</a><br/>

<a NAME="E2:59"/><b>then </b>
the <a href="msualg_1.html#U1">OperSymbols</a> of <font color="Maroon">S</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="instalg1.html#D1">INSTALG1:def 1</a></i>;<br/>
<a NAME="E3:59"/><b>then </b>
( the <a href="msualg_1.html#U2">Arity</a> of <font color="Maroon">S</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  &amp; the <a href="msualg_1.html#U3">ResultSort</a> of <font color="Maroon">S</font> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a>  )
 
<b>by </b><i><a class="ref" href="partfun1.html#T57">PARTFUN1:57</a></i>;<br/>
<a NAME="E4:59"/><b>then </b>
( the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">S</font> <a href="tarski.html#R1">c=</a> the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">T</font> &amp; the <a href="msualg_1.html#U2">Arity</a> of <font color="Maroon">S</font> <a href="tarski.html#R1">c=</a> the <a href="msualg_1.html#U2">Arity</a> of <font color="Maroon">T</font> &amp; the <a href="msualg_1.html#U3">ResultSort</a> of <font color="Maroon">S</font> <a href="tarski.html#R1">c=</a> the <a href="msualg_1.html#U3">ResultSort</a> of <font color="Maroon">T</font> )
 
<b>by </b><i><a class="ref" href="algspec1.html#T6" target="_self">Th6</a>, <a class="ref" href="xboole_1.html#T2">XBOOLE_1:2</a></i>;<br/>
<b>hence </b><a NAME="E5:59"/>
<font color="Maroon">S</font> is    <a href="instalg1.html#M1">Subsignature</a> of <font color="Maroon">T</font>
 <b>by </b><i><a class="ref" href="instalg1.html#T14">INSTALG1:14</a></i>; <i><font color="Red">:: according to </font></i><a class="ref" href="algspec1.html#D5" target="_self">ALGSPEC1:def 5</a><br/>


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