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<b>let </b><font color="Maroon">c<sub>1</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be   <a href="funct_1.html#NM1">Function</a>;<br/>



<b>assume </b><b>that </b><br/><a NAME="E1:118"/><i><font color="Green">E46</font></i>: 
<font color="Maroon">c<sub>1</sub></font> <a href="tarski.html#R1">c=</a>  <a href="relat_1.html#K1">dom</a> <font color="Maroon">c<sub>2</sub></font>
 <b>and </b><br/><a NAME="E2:118"/><i><font color="Green">E47</font></i>: 
<font color="Maroon">c<sub>2</sub></font> is <a href="funct_1.html#V2" target="_self">one-to-one</a>
 ;<br/>

<b>thus </b><a NAME="E3:118"/>
<font color="Maroon">c<sub>2</sub></font> <a href="relat_1.html#K10">"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="relat_1.html#K9">.:</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="tarski.html#R1">c=</a> <font color="Maroon">c<sub>1</sub></font>
 <b>by </b><i><a class="txt" href="funct_1.html#E2:118"><i><font color="Green">E47</font></i></a>, <a class="ref" href="funct_1.html#T152" target="_self">Th152</a></i>; <i><font color="Red">:: according to </font></i><a class="ref" href="xboole_0.html#D10">XBOOLE_0:def 10</a><br/>

<b>let </b><font color="Maroon">c<sub>3</sub></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="E4:118"/><i><font color="Green">E48</font></i>: 
<font color="Maroon">c<sub>3</sub></font> <a href="hidden.html#R2">in</a> <font color="Maroon">c<sub>1</sub></font>
 ;<br/>

<a NAME="E5:118"/><b>then </b>
<font color="Maroon">c<sub>2</sub></font> <a href="funct_1.html#K1" target="_self">.</a> <font color="Maroon">c<sub>3</sub></font> <a href="hidden.html#R2">in</a> <font color="Maroon">c<sub>2</sub></font> <a href="relat_1.html#K9">.:</a> <font color="Maroon">c<sub>1</sub></font>
 
<b>by </b><i><a class="txt" href="funct_1.html#E1:118"><i><font color="Green">E46</font></i></a>, <a class="ref" href="funct_1.html#D12" target="_self">Def12</a></i>;<br/>
<b>hence </b><a NAME="E6:118"/>
<font color="Maroon">c<sub>3</sub></font> <a href="hidden.html#R2">in</a> <font color="Maroon">c<sub>2</sub></font> <a href="relat_1.html#K10">"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="relat_1.html#K9">.:</a> <font color="Maroon">c<sub>1</sub></font></span>)</span>
 <b>by </b><i><a class="txt" href="funct_1.html#E1:118"><i><font color="Green">E46</font></i></a>, <a class="txt" href="funct_1.html#E4:118"><i><font color="Green">E48</font></i></a>, <a class="ref" href="funct_1.html#D13" target="_self">Def13</a></i>;<br/>


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