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<b>let </b><font color="Maroon">F1</font> be    <a href="fraenkel.html#M1">FUNCTION_DOMAIN</a> of the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">UA</font>,the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">UA</font>, <font color="Maroon">F2</font> be    <a href="fraenkel.html#M1">FUNCTION_DOMAIN</a> of the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">UA</font>,the <a href="struct_0.html#U1">carrier</a> of <font color="Maroon">UA</font>;<br/>

<b>assume </b><b>that </b><br/><a NAME="E1:2_1_2"/><i><font color="Green">E42</font></i>: 
( ( for <font color="Olive">f</font> being   <a href="fraenkel.html#M2">Element</a> of <font color="Maroon">F1</font> holds  <font color="Olive">f</font> is   <a href="struct_0.html#NM6">Function</a> of <font color="Maroon">UA</font>,<font color="Maroon">UA</font> ) &amp; ( for <font color="Olive">h</font> being  <a href="struct_0.html#NM6">Function</a> of <font color="Maroon">UA</font>,<font color="Maroon">UA</font> holds <br/> ( <font color="Olive">h</font> <a href="hidden.html#R2">in</a> <font color="Maroon">F1</font> iff <font color="Olive">h</font> <a href="alg_1.html#R4">is_isomorphism</a> <font color="Maroon">UA</font>,<font color="Maroon">UA</font> ) ) )
 <b>and </b><br/><a NAME="E2:2_1_2"/><i><font color="Green">E43</font></i>: 
( ( for <font color="Olive">f</font> being   <a href="fraenkel.html#M2">Element</a> of <font color="Maroon">F2</font> holds  <font color="Olive">f</font> is   <a href="struct_0.html#NM6">Function</a> of <font color="Maroon">UA</font>,<font color="Maroon">UA</font> ) &amp; ( for <font color="Olive">h</font> being  <a href="struct_0.html#NM6">Function</a> of <font color="Maroon">UA</font>,<font color="Maroon">UA</font> holds <br/> ( <font color="Olive">h</font> <a href="hidden.html#R2">in</a> <font color="Maroon">F2</font> iff <font color="Olive">h</font> <a href="alg_1.html#R4">is_isomorphism</a> <font color="Maroon">UA</font>,<font color="Maroon">UA</font> ) ) )
 ;<br/>

<a NAME="E3:2_1_2"/><i><font color="Green">E44</font></i>: 
<font color="Maroon">F1</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">F2</font>
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="2_1_2_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">q</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:2_1_2_1"/><i><font color="Green">E45</font></i>: 
<font color="Maroon">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">F1</font>
 ;<br/>

<b>then reconsider </b><font color="Maroon">h1</font> = <font color="Maroon">q</font> as   <a href="struct_0.html#NM6">Function</a> of <font color="Maroon">UA</font>,<font color="Maroon">UA</font> <b>by </b><i/>;<br/>
<a NAME="E3:2_1_2_1"/>
<font color="Maroon">h1</font> <a href="alg_1.html#R4">is_isomorphism</a> <font color="Maroon">UA</font>,<font color="Maroon">UA</font>
 
<b>by </b><i>, </i>;<br/>
<b>hence </b><a NAME="E4:2_1_2_1"/>
<font color="Maroon">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">F2</font>
 <b>by </b><i/>;<br/>


</div><b>end;</b></div>
<a NAME="E4:2_1_2"/>
<font color="Maroon">F2</font> <a href="tarski.html#R1">c=</a> <font color="Maroon">F1</font>
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="2_1_2_2"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon">q</font> be    <a href="hidden.html#M1">set</a> ; <i><font color="Red">:: according to </font></i><a class="ref" href="tarski.html#D3">TARSKI:def 3</a><br/>

<b>assume </b><a NAME="E1:2_1_2_2"/><i><font color="Green">E47</font></i>: 
<font color="Maroon">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">F2</font>
 ;<br/>

<b>then reconsider </b><font color="Maroon">h1</font> = <font color="Maroon">q</font> as   <a href="struct_0.html#NM6">Function</a> of <font color="Maroon">UA</font>,<font color="Maroon">UA</font> <b>by </b><i/>;<br/>
<a NAME="E3:2_1_2_2"/>
<font color="Maroon">h1</font> <a href="alg_1.html#R4">is_isomorphism</a> <font color="Maroon">UA</font>,<font color="Maroon">UA</font>
 
<b>by </b><i>, </i>;<br/>
<b>hence </b><a NAME="E4:2_1_2_2"/>
<font color="Maroon">q</font> <a href="hidden.html#R2">in</a> <font color="Maroon">F1</font>
 <b>by </b><i/>;<br/>


</div><b>end;</b></div>
<b>hence </b><a NAME="E5:2_1_2"/>
<font color="Maroon">F1</font> <a href="hidden.html#R1">=</a> <font color="Maroon">F2</font>
 <b>by </b><i>, <a class="ref" href="xboole_0.html#D10">XBOOLE_0:def 10</a></i>;<br/>


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