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<b>let </b><font color="Maroon">c<sub>1</sub></font> be  non <a href="xboole_0.html#V1">empty</a>  <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be   <a href="matrix_1.html#NM1">Matrix</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>



<div><b>hereby </b>
<div class="add"><b>assume </b><a NAME="E1:19_1"/>
not <font color="Maroon">c<sub>2</sub></font> is <a href="relat_1.html#V3">empty-yielding</a>
 ;<br/><a NAME="E2:19_1"/><b>then </b>
( 0 <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>2</sub></font> &amp; 0 <a href="hidden.html#NR2" target="_self">&lt;&gt;</a>  <a href="matrix_1.html#K1">width</a> <font color="Maroon">c<sub>2</sub></font> )
 <b>by </b><i><a class="ref" href="goboard1.html#D5" target="_self">Def5</a></i>;<br/><b>hence </b><a NAME="E3:19_1"/>
( 0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>2</sub></font> &amp; 0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a>  <a href="matrix_1.html#K1">width</a> <font color="Maroon">c<sub>2</sub></font> )
 ;<br/></div>
<b>end;</b></div>

<b>assume </b><a NAME="E2:19"/>
( 0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a>  <a href="finseq_1.html#K3">len</a> <font color="Maroon">c<sub>2</sub></font> &amp; 0 <a href="xxreal_0.html#NR3" target="_self">&lt;</a>  <a href="matrix_1.html#K1">width</a> <font color="Maroon">c<sub>2</sub></font> )
 ;<br/>

<b>hence </b><a NAME="E3:19"/>
not <font color="Maroon">c<sub>2</sub></font> is <a href="relat_1.html#V3">empty-yielding</a>
 <b>by </b><i><a class="ref" href="goboard1.html#D5" target="_self">Def5</a></i>;<br/>


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