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<b>let </b><font color="Maroon" title="c1">Y</font> be  non <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>  <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/><b>let </b><font color="Maroon" title="c2">a</font>, <font color="Maroon" title="c3">b</font>, <font color="Maroon" title="c4">c</font> be    <a href="fraenkel.html#M2" title="FRAENKEL:mode.2">Element</a> of  <a href="fraenkel.html#K1" title="FRAENKEL:func.1">Funcs</a> <font color="Maroon" title="c1">Y</font>,<a href="margrel1.html#K6" title="MARGREL1:func.6">BOOLEAN</a> ;<br/>



<b>reconsider </b><font color="Maroon" title="c5">a'</font> = <font color="Maroon" title="c2">a</font>, <font color="Maroon" title="c6">b'</font> = <font color="Maroon" title="c3">b</font>, <font color="Maroon" title="c7">c'</font> = <font color="Maroon" title="c4">c</font> as    <a href="fraenkel.html#M2" title="FRAENKEL:mode.2">Element</a> of  <a href="fraenkel.html#K1" title="FRAENKEL:func.1">Funcs</a> <font color="Maroon" title="c1">Y</font>,<a href="margrel1.html#K6" title="MARGREL1:func.6">BOOLEAN</a>  ;<br/>
<a NAME="E2:19"/><i><font color="Green" title="E12">A1</font></i>: 
for <font color="Olive" title="b1">x</font> being   <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Maroon" title="c1">Y</font> holds  <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c6">b'</font></span>)</span> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c7">c'</font></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Olive" title="b1">x</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <span class="p2">(<span class="default"><font color="Maroon" title="c6">b'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c7">c'</font></span>)</span></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Olive" title="b1">x</font>
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="19_1"><b>proof </b></a><div class="add">

<b>let </b><font color="Maroon" title="c8">x</font> be    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of <font color="Maroon" title="c1">Y</font>;<br/>

<a NAME="E1:19_1"/><i><font color="Green" title="E13">A2</font></i>: 
<span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <span class="p2">(<span class="default"><font color="Maroon" title="c6">b'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c7">c'</font></span>)</span></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon" title="c6">b'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c7">c'</font></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span>
 
<b>by </b><i><a class="ref" href="margrel1.html#D21" title="MARGREL1:def.21">MARGREL1:def 21</a></i>;<br/>
<a NAME="E2:19_1"/><i><font color="Green" title="E14">A3</font></i>: 
<span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon" title="c6">b'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c7">c'</font></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon" title="c6">b'</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p2">(<span class="default"><font color="Maroon" title="c7">c'</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span></span>)</span>
 
<b>by </b><i><a class="ref" href="margrel1.html#D21" title="MARGREL1:def.21">MARGREL1:def 21</a></i>;<br/>
<a NAME="E3:19_1"/><i><font color="Green" title="E15">A4</font></i>: 
<span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon" title="c3">b</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p2">(<span class="default"><font color="Maroon" title="c4">c</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon" title="c2">a</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p2">(<span class="default"><font color="Maroon" title="c3">b</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p1">(<span class="default"><font color="Maroon" title="c4">c</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span>
 
;<br/>
<a NAME="E4:19_1"/>
<span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="margrel1.html#K10" title="MARGREL1:func.10">'&amp;'</a> <span class="p1">(<span class="default"><font color="Maroon" title="c6">b'</font> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c6">b'</font></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font>
 
<b>by </b><i><a class="ref" href="margrel1.html#D21" title="MARGREL1:def.21">MARGREL1:def 21</a></i>;<br/>
<b>hence </b><a NAME="E5:19_1"/>
<span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c6">b'</font></span>)</span> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c7">c'</font></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><font color="Maroon" title="c5">a'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <span class="p2">(<span class="default"><font color="Maroon" title="c6">b'</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c7">c'</font></span>)</span></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c8">x</font>
 <b>by </b><i><a class="txt" href="bvfunc_1.html#E1:19_1"><i><font color="Green" title="E13">A2</font></i></a>, <a class="txt" href="bvfunc_1.html#E2:19_1"><i><font color="Green" title="E14">A3</font></i></a>, <a class="txt" href="bvfunc_1.html#E3:19_1"><i><font color="Green" title="E15">A4</font></i></a>, <a class="ref" href="margrel1.html#D21" title="MARGREL1:def.21">MARGREL1:def 21</a></i>;<br/>


</div><b>end;</b></div>
<b>consider </b><font color="Maroon" title="c8">k3</font> being   <a href="funct_1.html#NM1" title="FUNCT_1:NM.1">Function</a><b> such that </b><br/><a NAME="E4:19"/><i><font color="Green" title="E13">A5</font></i>: 
( <span class="p1">(<span class="default"><font color="Maroon" title="c2">a</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c3">b</font></span>)</span> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c4">c</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c8">k3</font> &amp;  <a href="relat_1.html#K1" title="RELAT_1:func.1">dom</a> <font color="Maroon" title="c8">k3</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c1">Y</font> &amp;  <a href="relat_1.html#K2" title="RELAT_1:func.2">rng</a> <font color="Maroon" title="c8">k3</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="margrel1.html#K6" title="MARGREL1:func.6">BOOLEAN</a>  )
 <b>by </b><i><a class="ref" href="funct_2.html#D2" title="FUNCT_2:def.2">FUNCT_2:def 2</a></i>;<br/>
<b>consider </b><font color="Maroon" title="c9">k4</font> being   <a href="funct_1.html#NM1" title="FUNCT_1:NM.1">Function</a><b> such that </b><br/><a NAME="E6:19"/><i><font color="Green" title="E14">A6</font></i>: 
( <font color="Maroon" title="c2">a</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <span class="p1">(<span class="default"><font color="Maroon" title="c3">b</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c4">c</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c9">k4</font> &amp;  <a href="relat_1.html#K1" title="RELAT_1:func.1">dom</a> <font color="Maroon" title="c9">k4</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c1">Y</font> &amp;  <a href="relat_1.html#K2" title="RELAT_1:func.2">rng</a> <font color="Maroon" title="c9">k4</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="margrel1.html#K6" title="MARGREL1:func.6">BOOLEAN</a>  )
 <b>by </b><i><a class="ref" href="funct_2.html#D2" title="FUNCT_2:def.2">FUNCT_2:def 2</a></i>;<br/>
<a NAME="E7:19"/>
for <font color="Olive" title="b1">u</font> being   <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a>   st <font color="Olive" title="b1">u</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c1">Y</font> holds <br/><font color="Maroon" title="c8">k3</font> <a href="funct_1.html#K1" title="FUNCT_1:func.1">.</a> <font color="Olive" title="b1">u</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c9">k4</font> <a href="funct_1.html#K1" title="FUNCT_1:func.1">.</a> <font color="Olive" title="b1">u</font>
 
<b>by </b><i><a class="txt" href="bvfunc_1.html#E2:19"><i><font color="Green" title="E12">A1</font></i></a>, <a class="txt" href="bvfunc_1.html#E4:19"><i><font color="Green" title="E13">A5</font></i></a>, <a class="txt" href="bvfunc_1.html#E6:19"><i><font color="Green" title="E14">A6</font></i></a></i>;<br/>
<b>hence </b><a NAME="E8:19"/>
<span class="p1">(<span class="default"><font color="Maroon" title="c2">a</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c3">b</font></span>)</span> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c4">c</font> <a href="funct_2.html#R2" title="FUNCT_2:pred.2">=</a> <font color="Maroon" title="c2">a</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <span class="p1">(<span class="default"><font color="Maroon" title="c3">b</font> <a href="margrel1.html#K16" title="MARGREL1:func.16">'&amp;'</a> <font color="Maroon" title="c4">c</font></span>)</span>
 <b>by </b><i><a class="txt" href="bvfunc_1.html#E4:19"><i><font color="Green" title="E13">A5</font></i></a>, <a class="txt" href="bvfunc_1.html#E6:19"><i><font color="Green" title="E14">A6</font></i></a>, <a class="ref" href="funct_1.html#T9" title="FUNCT_1:th.9">FUNCT_1:9</a></i>;<br/>


</div>
