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<b>let </b><font color="Maroon" title="c1">A</font> be   <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <span class="p1">(<span class="default"><a href="euclid.html#K15" title="EUCLID:func.15">TOP-REAL</a> 2</span>)</span>; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> ( <font color="Maroon" title="c1">A</font> is <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a> implies <font color="Maroon" title="c1">A</font> is <a href="sppol_1.html#V1" title="SPPOL_1:attr.1">horizontal</a> )</span><br/>

<b>assume </b><a NAME="E1:38_1_1"/><i><font color="Green" title="E20">A1</font></i>: 
<font color="Maroon" title="c1">A</font> is <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>
 ; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> <font color="Maroon" title="c1">A</font> is <a href="sppol_1.html#V1" title="SPPOL_1:attr.1">horizontal</a></span><br/>

<b>assume </b><a NAME="E2:38_1_1"/>
not <font color="Maroon" title="c1">A</font> is <a href="sppol_1.html#V1" title="SPPOL_1:attr.1">horizontal</a>
 ; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> contradiction</span><br/>

<b>then reconsider </b><font color="Maroon" title="c2">B</font> = <font color="Maroon" title="c1">A</font> as  non <a href="sppol_1.html#V1" title="SPPOL_1:attr.1">horizontal</a> <a href="struct_0.html#NM2" title="STRUCT_0:NM.2">Subset</a> of <span class="p1">(<span class="default"><a href="euclid.html#K15" title="EUCLID:func.15">TOP-REAL</a> 2</span>)</span> ;<br/>
<a NAME="E4:38_1_1"/>
not <font color="Maroon" title="c2">B</font> is <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>
 
;<br/>
<b>hence </b><a NAME="E5:38_1_1"/>
contradiction
 <b>by </b><i><a class="txt" href="topreal6.html#E1:38_1_1"><i><font color="Green" title="E20">A1</font></i></a></i>; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> verum</span><br/>


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