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<b>let </b><font color="Maroon">c<sub>3</sub></font>, <font color="Maroon">c<sub>4</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="E1:9_1_1"/><i><font color="Green">E10</font></i>: 
<font color="Maroon">c<sub>3</sub></font> <a href="sheffer1.html#R1" target="_self">is_a_complement'_of</a> <font color="Maroon">c<sub>2</sub></font>
 <b>and </b><br/><a NAME="E2:9_1_1"/><i><font color="Green">E11</font></i>: 
<font color="Maroon">c<sub>4</sub></font> <a href="sheffer1.html#R1" target="_self">is_a_complement'_of</a> <font color="Maroon">c<sub>2</sub></font>
 ;<br/>

<font color="Maroon">c<sub>4</sub></font> = 
<font color="Maroon">c<sub>4</sub></font> <a href="lattices.html#K2">"/\"</a> <span class="p1">(<span class="default"><a href="sheffer1.html#K1" target="_self">Top'</a> <font color="Maroon">c<sub>1</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E1:9"><i><font color="Green">E9</font></i></a>, <a class="ref" href="sheffer1.html#D2" target="_self">Def2</a></i>
<br/>.= 
<font color="Maroon">c<sub>4</sub></font> <a href="lattices.html#K2">"/\"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="lattices.html#K1">"\/"</a> <font color="Maroon">c<sub>3</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E1:9_1_1"><i><font color="Green">E10</font></i></a>, <a class="ref" href="sheffer1.html#D6" target="_self">Def6</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="lattices.html#K1">"\/"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>3</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E1:9"><i><font color="Green">E9</font></i></a>, <a class="ref" href="lattices.html#D11">LATTICES:def 11</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>4</sub></font></span>)</span> <a href="lattices.html#K1">"\/"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>4</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>3</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E1:9"><i><font color="Green">E9</font></i></a>, <a class="ref" href="lattices.html#D6">LATTICES:def 6</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>4</sub></font></span>)</span> <a href="lattices.html#K1">"\/"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>3</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>4</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E1:9"><i><font color="Green">E9</font></i></a>, <a class="ref" href="lattices.html#D6">LATTICES:def 6</a></i>
<br/>.= 
<span class="p1">(<span class="default"><a href="sheffer1.html#K2" target="_self">Bot'</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="lattices.html#K1">"\/"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>3</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>4</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E2:9_1_1"><i><font color="Green">E11</font></i></a>, <a class="ref" href="sheffer1.html#D6" target="_self">Def6</a></i>
<br/>.= 
<span class="p1">(<span class="default"><font color="Maroon">c<sub>3</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>2</sub></font></span>)</span> <a href="lattices.html#K1">"\/"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>3</sub></font> <a href="lattices.html#K2">"/\"</a> <font color="Maroon">c<sub>4</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E1:9_1_1"><i><font color="Green">E10</font></i></a>, <a class="ref" href="sheffer1.html#D6" target="_self">Def6</a></i>
<br/>.= 
<font color="Maroon">c<sub>3</sub></font> <a href="lattices.html#K2">"/\"</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="lattices.html#K1">"\/"</a> <font color="Maroon">c<sub>4</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E1:9"><i><font color="Green">E9</font></i></a>, <a class="ref" href="lattices.html#D11">LATTICES:def 11</a></i>
<br/>.= 
<font color="Maroon">c<sub>3</sub></font> <a href="lattices.html#K2">"/\"</a> <span class="p1">(<span class="default"><a href="sheffer1.html#K1" target="_self">Top'</a> <font color="Maroon">c<sub>1</sub></font></span>)</span>
<b>by </b><i><a class="txt" href="sheffer1.html#E2:9_1_1"><i><font color="Green">E11</font></i></a>, <a class="ref" href="sheffer1.html#D6" target="_self">Def6</a></i>
<br/>.= 
<font color="Maroon">c<sub>3</sub></font>
<b>by </b><i><a class="txt" href="sheffer1.html#E1:9"><i><font color="Green">E9</font></i></a>, <a class="ref" href="sheffer1.html#D2" target="_self">Def2</a></i>
;<br/>
<b>hence </b><a NAME="E4:9_1_1"/>
<font color="Maroon">c<sub>3</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font>
 ;<br/>


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