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<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="card_1.html#NM1">Cardinal</a>;<br/>

<a NAME="E1:45"/>
 <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><a href="xboole_0.html#K1">{}</a>  <a href="funcop_1.html#K2">--&gt;</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 
;<br/>
<a NAME="E2:45"/><b>then </b>
 <a href="relat_1.html#K1">dom</a> <span class="p1">(<span class="default"><a href="card_3.html#K2" target="_self">disjoin</a> <span class="p2">(<span class="default"><a href="xboole_0.html#K1">{}</a>  <a href="funcop_1.html#K2">--&gt;</a> <font color="Maroon">c<sub>1</sub></font></span>)</span></span>)</span> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="card_3.html#D3" target="_self">Def3</a></i>;<br/>
<a NAME="E3:45"/><b>then </b>
 <a href="relat_1.html#K2">rng</a> <span class="p1">(<span class="default"><a href="card_3.html#K2" target="_self">disjoin</a> <span class="p2">(<span class="default"><a href="xboole_0.html#K1">{}</a>  <a href="funcop_1.html#K2">--&gt;</a> <font color="Maroon">c<sub>1</sub></font></span>)</span></span>)</span> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="relat_1.html#T65">RELAT_1:65</a></i>;<br/>
<a NAME="E4:45"/><b>then </b>
 <a href="card_3.html#K3" target="_self">Union</a> <span class="p1">(<span class="default"><a href="card_3.html#K2" target="_self">disjoin</a> <span class="p2">(<span class="default"><a href="xboole_0.html#K1">{}</a>  <a href="funcop_1.html#K2">--&gt;</a> <font color="Maroon">c<sub>1</sub></font></span>)</span></span>)</span> <a href="hidden.html#R1">=</a>  <a href="xboole_0.html#K1">{}</a> 
 
<b>by </b><i><a class="ref" href="zfmisc_1.html#T2">ZFMISC_1:2</a></i>;<br/>
<b>hence </b><a NAME="E5:45"/>
 <a href="card_3.html#K6" target="_self">Sum</a> <span class="p1">(<span class="default"><a href="xboole_0.html#K1">{}</a>  <a href="funcop_1.html#K2">--&gt;</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="hidden.html#R1">=</a> 0
 <b>by </b><i><a class="ref" href="card_1.html#T47">CARD_1:47</a></i>;<br/>


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