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<b>let </b><font color="Maroon" title="c1">Y0</font>, <font color="Maroon" title="c2">Y1</font> be    <a href="pre_topc.html#L1" title="PRE_TOPC:struct.1">TopStruct</a> ;<br/><b>let </b><font color="Maroon" title="c3">D0</font> be   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">Y0</font>;<br/><b>let </b><font color="Maroon" title="c4">D1</font> be   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c2">Y1</font>;<br/>





<b>assume </b><a NAME="E1:21"/><i><font color="Green" title="E14">A1</font></i>: 
 <a href="pre_topc.html#G1" title="PRE_TOPC:aggr.1">TopStruct</a>(# the <a href="struct_0.html#U1" title="STRUCT_0:sel.1">carrier</a> of <font color="Maroon" title="c1">Y0</font>,the <a href="pre_topc.html#U1" title="PRE_TOPC:sel.1">topology</a> of <font color="Maroon" title="c1">Y0</font> #) <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="pre_topc.html#G1" title="PRE_TOPC:aggr.1">TopStruct</a>(# the <a href="struct_0.html#U1" title="STRUCT_0:sel.1">carrier</a> of <font color="Maroon" title="c2">Y1</font>,the <a href="pre_topc.html#U1" title="PRE_TOPC:sel.1">topology</a> of <font color="Maroon" title="c2">Y1</font> #)
 ;<br/>

<b>assume </b><a NAME="E2:21"/><i><font color="Green" title="E15">A2</font></i>: 
<font color="Maroon" title="c3">D0</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c4">D1</font>
 ;<br/>

<b>assume </b><a NAME="E3:21"/><i><font color="Green" title="E16">A3</font></i>: 
<font color="Maroon" title="c3">D0</font> is <a href="tsp_1.html#V1" title="TSP_1:attr.1">T_0</a>
 ;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="21_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon" title="c5">x</font>, <font color="Maroon" title="c6">y</font> be   <a href="pre_topc.html#NM2" title="PRE_TOPC:NM.2">Point</a> of <font color="Maroon" title="c2">Y1</font>;<br/><b>assume </b><a NAME="E1:21_1"/><i><font color="Green" title="E17">A4</font></i>: 
( <font color="Maroon" title="c5">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c4">D1</font> &amp; <font color="Maroon" title="c6">y</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c4">D1</font> )
 ;<br/><b>assume </b><a NAME="E2:21_1"/><i><font color="Green" title="E18">A5</font></i>: 
<font color="Maroon" title="c5">x</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a> <font color="Maroon" title="c6">y</font>
 ;<br/><b>reconsider </b><font color="Maroon" title="c7">x0</font> = <font color="Maroon" title="c5">x</font>, <font color="Maroon" title="c8">y0</font> = <font color="Maroon" title="c6">y</font> as   <a href="pre_topc.html#NM2" title="PRE_TOPC:NM.2">Point</a> of <font color="Maroon" title="c1">Y0</font> <b>by </b><i><a class="txt" href="tsp_1.html#E1:21"><i><font color="Green" title="E14">A1</font></i></a></i>;<br/><div><b>hereby </b>
<div class="add"><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="21_1_1_1"><b>per </b></a><a class="txt" onclick="hs(this)" href="javascript:()"><b>cases </b></a><span class="hide"><a NAME="E1:21_1_1_1"/>
(  ex <font color="Olive" title="b1">V</font> being  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">Y0</font> st <br/>( <font color="Olive" title="b1">V</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a> &amp; <font color="Maroon" title="c7">x0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">V</font> &amp; not <font color="Maroon" title="c8">y0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">V</font> ) or  ex <font color="Olive" title="b1">W</font> being  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">Y0</font> st <br/>( <font color="Olive" title="b1">W</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a> &amp; not <font color="Maroon" title="c7">x0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">W</font> &amp; <font color="Maroon" title="c8">y0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">W</font> ) )
 </span><b>by </b><i><a class="txt" href="tsp_1.html#E2:21"><i><font color="Green" title="E15">A2</font></i></a>, <a class="txt" href="tsp_1.html#E3:21"><i><font color="Green" title="E16">A3</font></i></a>, <a class="txt" href="tsp_1.html#E1:21_1"><i><font color="Green" title="E17">A4</font></i></a>, <a class="txt" href="tsp_1.html#E2:21_1"><i><font color="Green" title="E18">A5</font></i></a>, <a class="ref" href="tsp_1.html#D8" target="_self" title="TSP_1:def.8">Def8</a></i>;<br/><div class="add"><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="21_1_1_1_1"><b>suppose </b></a><a NAME="E1:21_1_1_1_1"/>
 ex <font color="Olive" title="b1">V</font> being  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">Y0</font> st <br/>( <font color="Olive" title="b1">V</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a> &amp; <font color="Maroon" title="c7">x0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">V</font> &amp; not <font color="Maroon" title="c8">y0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">V</font> )
 ;<br/><div class="add"><b>then consider </b><font color="Maroon" title="c9">V</font> being   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">Y0</font><b> such that </b><br/><a NAME="E3:21_1_1_1_1"/><i><font color="Green" title="E19">A6</font></i>: 
<font color="Maroon" title="c9">V</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a>
 <b>and </b><br/><a NAME="E4:21_1_1_1_1"/><i><font color="Green" title="E20">A7</font></i>: 
( <font color="Maroon" title="c7">x0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c9">V</font> &amp; not <font color="Maroon" title="c8">y0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c9">V</font> )
 ;<br/><b>reconsider </b><font color="Maroon" title="c10">V1</font> = <font color="Maroon" title="c9">V</font> as   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c2">Y1</font> <b>by </b><i><a class="txt" href="tsp_1.html#E1:21"><i><font color="Green" title="E14">A1</font></i></a></i>;<br/><div><a class="txt" onclick="hs2(this)" href="javascript:()" title="21_1_1_1_1_1"><b>now </b></a><div class="add"><b>take </b><font color="Maroon" title="c11">V1</font> = <font color="Maroon" title="c10">V1</font>;<br/><a NAME="E1:21_1_1_1_1_1"/>
<font color="Maroon" title="c11">V1</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> the <a href="pre_topc.html#U1" title="PRE_TOPC:sel.1">topology</a> of <font color="Maroon" title="c2">Y1</font>
 <b>by </b><i><a class="txt" href="tsp_1.html#E1:21"><i><font color="Green" title="E14">A1</font></i></a>, <a class="txt" href="tsp_1.html#E3:21_1_1_1_1"><i><font color="Green" title="E19">A6</font></i></a>, <a class="ref" href="pre_topc.html#D5" title="PRE_TOPC:def.5">PRE_TOPC:def 5</a></i>;<br/><b>hence </b><a NAME="E2:21_1_1_1_1_1"/>
<font color="Maroon" title="c11">V1</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a>
 <b>by </b><i><a class="ref" href="pre_topc.html#D5" title="PRE_TOPC:def.5">PRE_TOPC:def 5</a></i>;<br/><b>thus </b><a NAME="E3:21_1_1_1_1_1"/>
( <font color="Maroon" title="c5">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c11">V1</font> &amp; not <font color="Maroon" title="c6">y</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c11">V1</font> )
 <b>by </b><i><a class="txt" href="tsp_1.html#E4:21_1_1_1_1"><i><font color="Green" title="E20">A7</font></i></a></i>;<br/></div><b>end;</b></div><b>hence </b><a NAME="E7:21_1_1_1_1"/>
(  ex <font color="Olive" title="b1">V1</font> being  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c2">Y1</font> st <br/>( <font color="Olive" title="b1">V1</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a> &amp; <font color="Maroon" title="c5">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">V1</font> &amp; not <font color="Maroon" title="c6">y</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">V1</font> ) or  ex <font color="Olive" title="b1">W1</font> being  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c2">Y1</font> st <br/>( <font color="Olive" title="b1">W1</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a> &amp; not <font color="Maroon" title="c5">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">W1</font> &amp; <font color="Maroon" title="c6">y</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">W1</font> ) )
 ;<br/></div><b>end;</b></div><div><a class="txt" onclick="hsNdiv(this)" href="javascript:()" title="21_1_1_1_2"><b>suppose </b></a><a NAME="E1:21_1_1_1_2"/>
 ex <font color="Olive" title="b1">W</font> being  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">Y0</font> st <br/>( <font color="Olive" title="b1">W</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a> &amp; not <font color="Maroon" title="c7">x0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">W</font> &amp; <font color="Maroon" title="c8">y0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">W</font> )
 ;<br/><div class="add"><b>then consider </b><font color="Maroon" title="c9">W</font> being   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c1">Y0</font><b> such that </b><br/><a NAME="E3:21_1_1_1_2"/><i><font color="Green" title="E19">A8</font></i>: 
<font color="Maroon" title="c9">W</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a>
 <b>and </b><br/><a NAME="E4:21_1_1_1_2"/><i><font color="Green" title="E20">A9</font></i>: 
( not <font color="Maroon" title="c7">x0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c9">W</font> &amp; <font color="Maroon" title="c8">y0</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c9">W</font> )
 ;<br/><b>reconsider </b><font color="Maroon" title="c10">W1</font> = <font color="Maroon" title="c9">W</font> as   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c2">Y1</font> <b>by </b><i><a class="txt" href="tsp_1.html#E1:21"><i><font color="Green" title="E14">A1</font></i></a></i>;<br/><div><a class="txt" onclick="hs2(this)" href="javascript:()" title="21_1_1_1_2_1"><b>now </b></a><div class="add"><b>take </b><font color="Maroon" title="c11">W1</font> = <font color="Maroon" title="c10">W1</font>;<br/><a NAME="E1:21_1_1_1_2_1"/>
<font color="Maroon" title="c11">W1</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> the <a href="pre_topc.html#U1" title="PRE_TOPC:sel.1">topology</a> of <font color="Maroon" title="c2">Y1</font>
 <b>by </b><i><a class="txt" href="tsp_1.html#E1:21"><i><font color="Green" title="E14">A1</font></i></a>, <a class="txt" href="tsp_1.html#E3:21_1_1_1_2"><i><font color="Green" title="E19">A8</font></i></a>, <a class="ref" href="pre_topc.html#D5" title="PRE_TOPC:def.5">PRE_TOPC:def 5</a></i>;<br/><b>hence </b><a NAME="E2:21_1_1_1_2_1"/>
<font color="Maroon" title="c11">W1</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a>
 <b>by </b><i><a class="ref" href="pre_topc.html#D5" title="PRE_TOPC:def.5">PRE_TOPC:def 5</a></i>;<br/><b>thus </b><a NAME="E3:21_1_1_1_2_1"/>
( not <font color="Maroon" title="c5">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c11">W1</font> &amp; <font color="Maroon" title="c6">y</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Maroon" title="c11">W1</font> )
 <b>by </b><i><a class="txt" href="tsp_1.html#E4:21_1_1_1_2"><i><font color="Green" title="E20">A9</font></i></a></i>;<br/></div><b>end;</b></div><b>hence </b><a NAME="E7:21_1_1_1_2"/>
(  ex <font color="Olive" title="b1">V1</font> being  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c2">Y1</font> st <br/>( <font color="Olive" title="b1">V1</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a> &amp; <font color="Maroon" title="c5">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">V1</font> &amp; not <font color="Maroon" title="c6">y</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">V1</font> ) or  ex <font color="Olive" title="b1">W1</font> being  <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <font color="Maroon" title="c2">Y1</font> st <br/>( <font color="Olive" title="b1">W1</font> is <a href="pre_topc.html#V3" title="PRE_TOPC:attr.3">open</a> &amp; not <font color="Maroon" title="c5">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">W1</font> &amp; <font color="Maroon" title="c6">y</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a> <font color="Olive" title="b1">W1</font> ) )
 ;<br/></div><b>end;</b></div></div><b>end;</b></div></div>
<b>end;</b></div></div><b>end;</b></div>
<b>hence </b><a NAME="E5:21"/>
<font color="Maroon" title="c4">D1</font> is <a href="tsp_1.html#V1" title="TSP_1:attr.1">T_0</a>
 <b>by </b><i><a class="ref" href="tsp_1.html#D8" target="_self" title="TSP_1:def.8">Def8</a></i>;<br/>


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