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<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="dirort.html#NM1">Oriented_Orthogonality_Space</a>;<br/>

<b>assume </b><a NAME="E1:23"/><i><font color="Green">E13</font></i>: 
<font color="Maroon">c<sub>1</sub></font> is <a href="dirort.html#V2" target="_self">bach_transitive</a>
 ;<br/>

<b>let </b><font color="Maroon">c<sub>2</sub></font>, <font color="Maroon">c<sub>3</sub></font>, <font color="Maroon">c<sub>4</sub></font>, <font color="Maroon">c<sub>5</sub></font>, <font color="Maroon">c<sub>6</sub></font>, <font color="Maroon">c<sub>7</sub></font> be   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>











<b>assume </b><b>that </b><br/><a NAME="E2:23"/><i><font color="Green">E14</font></i>: 
<font color="Maroon">c<sub>2</sub></font>,<font color="Maroon">c<sub>3</sub></font> <a href="dirort.html#R2" target="_self">//</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>5</sub></font>
 <b>and </b><br/><a NAME="E3:23"/><i><font color="Green">E15</font></i>: 
<font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>5</sub></font> <a href="dirort.html#R2" target="_self">//</a> <font color="Maroon">c<sub>6</sub></font>,<font color="Maroon">c<sub>7</sub></font>
 <b>and </b><br/><a NAME="E4:23"/><i><font color="Green">E16</font></i>: 
<font color="Maroon">c<sub>4</sub></font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">c<sub>5</sub></font>
 ;<br/>

<b>consider </b><font color="Maroon">c<sub>8</sub></font>, <font color="Maroon">c<sub>9</sub></font> being   <a href="struct_0.html#NM1">Element</a> of <font color="Maroon">c<sub>1</sub></font><b> such that </b><br/><a NAME="E6:23"/><i><font color="Green">E17</font></i>: 
<font color="Maroon">c<sub>8</sub></font> <a href="hidden.html#NR2" target="_self">&lt;&gt;</a> <font color="Maroon">c<sub>9</sub></font>
 <b>and </b><br/><a NAME="E7:23"/><i><font color="Green">E18</font></i>: 
<font color="Maroon">c<sub>8</sub></font>,<font color="Maroon">c<sub>9</sub></font> <a href="dirort.html#NR1" target="_self">'//'</a> <font color="Maroon">c<sub>2</sub></font>,<font color="Maroon">c<sub>3</sub></font>
 <b>and </b><br/><a NAME="E8:23"/><i><font color="Green">E19</font></i>: 
<font color="Maroon">c<sub>8</sub></font>,<font color="Maroon">c<sub>9</sub></font> <a href="dirort.html#NR1" target="_self">'//'</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>5</sub></font>
 <b>by </b><i><a class="txt" href="dirort.html#E2:23"><i><font color="Green">E14</font></i></a>, <a class="ref" href="dirort.html#D3" target="_self">Def3</a></i>;<br/>
<a NAME="E9:23"/>
<font color="Maroon">c<sub>8</sub></font>,<font color="Maroon">c<sub>9</sub></font> <a href="dirort.html#NR1" target="_self">'//'</a> <font color="Maroon">c<sub>6</sub></font>,<font color="Maroon">c<sub>7</sub></font>
 
<b>by </b><i><a class="txt" href="dirort.html#E1:23"><i><font color="Green">E13</font></i></a>, <a class="txt" href="dirort.html#E3:23"><i><font color="Green">E15</font></i></a>, <a class="txt" href="dirort.html#E4:23"><i><font color="Green">E16</font></i></a>, <a class="txt" href="dirort.html#E8:23"><i><font color="Green">E19</font></i></a>, <a class="ref" href="dirort.html#T13" target="_self">Th13</a></i>;<br/>
<b>hence </b><a NAME="E10:23"/>
<font color="Maroon">c<sub>2</sub></font>,<font color="Maroon">c<sub>3</sub></font> <a href="dirort.html#R2" target="_self">//</a> <font color="Maroon">c<sub>6</sub></font>,<font color="Maroon">c<sub>7</sub></font>
 <b>by </b><i><a class="txt" href="dirort.html#E6:23"><i><font color="Green">E17</font></i></a>, <a class="txt" href="dirort.html#E7:23"><i><font color="Green">E18</font></i></a>, <a class="ref" href="dirort.html#D3" target="_self">Def3</a></i>;<br/>


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