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<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="relat_1.html#NM1">Relation</a>;<br/>

<b>assume </b><a NAME="E1:43_1_1"/>
<font color="Maroon">c<sub>1</sub></font> is <a href="seqm_3.html#V6">natural-yielding</a>
 ;<br/>

<a NAME="E2:43_1_1"/><b>then </b>
 <a href="relat_1.html#K2">rng</a> <font color="Maroon">c<sub>1</sub></font> <a href="tarski.html#R1">c=</a>  <a href="numbers.html#K5">NAT</a> 
 
<b>by </b><i><a class="ref" href="seqm_3.html#D8">SEQM_3:def 8</a></i>;<br/>
<a NAME="E3:43_1_1"/><b>then </b>
 <a href="relat_1.html#K2">rng</a> <font color="Maroon">c<sub>1</sub></font> <a href="tarski.html#R1">c=</a>  <a href="numbers.html#K2">COMPLEX</a> 
 
<b>by </b><i><a class="ref" href="numbers.html#T20">NUMBERS:20</a>, <a class="ref" href="xboole_1.html#T1">XBOOLE_1:1</a></i>;<br/>
<b>hence </b><a NAME="E4:43_1_1"/>
<font color="Maroon">c<sub>1</sub></font> is <a href="rvsum_1.html#V1">complex-yielding</a>
 <b>by </b><i><a class="ref" href="rvsum_1.html#D11">RVSUM_1:def 11</a></i>;<br/>


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