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<b>let </b><font color="Maroon">SAS</font> be   <a href="semi_af1.html#NM1">Semi_Affine_Space</a>;<br/><b>let </b><font color="Maroon">a</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">SAS</font>;<br/><b>let </b><font color="Maroon">b</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">SAS</font>;<br/><b>let </b><font color="Maroon">c</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">SAS</font>;<br/><b>let </b><font color="Maroon">d</font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">SAS</font>;<br/>









<b>assume </b><a NAME="E1:69"/>
 <a href="semi_af1.html#R3" target="_self">congr</a> <font color="Maroon">a</font>,<font color="Maroon">b</font>,<font color="Maroon">c</font>,<font color="Maroon">d</font>
 ;<br/>

<a NAME="E2:69"/><b>then </b>
(  <a href="semi_af1.html#R3" target="_self">congr</a> <font color="Maroon">a</font>,<font color="Maroon">b</font>,<font color="Maroon">c</font>,<font color="Maroon">d</font> &amp;  <a href="semi_af1.html#R3" target="_self">congr</a> <font color="Maroon">a</font>,<font color="Maroon">b</font>,<font color="Maroon">a</font>,<font color="Maroon">b</font> )
 
<b>by </b><i><a class="ref" href="semi_af1.html#T28" target="_self">Th28</a></i>;<br/>
<b>hence </b><a NAME="E3:69"/>
 <a href="semi_af1.html#R3" target="_self">congr</a> <font color="Maroon">c</font>,<font color="Maroon">d</font>,<font color="Maroon">a</font>,<font color="Maroon">b</font>
 <b>by </b><i><a class="ref" href="semi_af1.html#T29" target="_self">Th29</a></i>;<br/>


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