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<b>let </b><font color="Maroon" title="c1">Y</font> be  non <a href="xboole_0.html#V1" title="XBOOLE_0:attr.1">empty</a>  <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> <span class="p1">(<span class="default"><a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font></span>)</span> <a href="bvfunc_1.html#K13" title="BVFUNC_1:func.13">'eqv'</a> <span class="p1">(<span class="default"><a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font></span>)</span> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font></span><br/>

<b>thus </b><span class="p1">(<span class="default"><a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font></span>)</span> <a href="bvfunc_1.html#K13" title="BVFUNC_1:func.13">'eqv'</a> <span class="p1">(<span class="default"><a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font></span>)</span> = 
 <a href="margrel1.html#K15" title="MARGREL1:func.15">'not'</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font></span>)</span> <a href="bvfunc_1.html#K7" title="BVFUNC_1:func.7">'xor'</a> <span class="p2">(<span class="default"><a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font></span>)</span></span>)</span>
<b>by </b><i><a class="ref" href="bvfunc25.html#T12" title="BVFUNC25:th.12">BVFUNC25:12</a></i>
<br/>.= 
 <a href="margrel1.html#K15" title="MARGREL1:func.15">'not'</a> <span class="p1">(<span class="default"><a href="margrel1.html#K15" title="MARGREL1:func.15">'not'</a> <span class="p2">(<span class="default"><a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font></span>)</span></span>)</span>
<b>by </b><i><a class="ref" href="bvfunc_8.html#T14" title="BVFUNC_8:th.14">BVFUNC_8:14</a></i>
<br/>.= 
 <a href="bvfunc_1.html#K17" title="BVFUNC_1:func.17">I_el</a> <font color="Maroon" title="c1">Y</font>

; <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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