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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="xreal_0.html#V1">real</a>  <a href="ordinal1.html#NM1" target="_self">number</a> ;<br/>

<a NAME="E1:3"/>
2 <a href="hidden.html#R1">=</a> 1 <a href="nat_1.html#K2">*</a> 2
 
;<br/>
<a NAME="E2:3"/><b>then </b>
2 is <a href="abian.html#V1">even</a>
 
<b>by </b><i><a class="ref" href="abian.html#D2">ABIAN:def 2</a></i>;<br/>
<b>hence </b><a NAME="E3:3"/>
<font color="Maroon">c<sub>1</sub></font> <a href="power.html#K3">to_power</a> 2 <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><a href="xcmplx_0.html#K4">-</a> <font color="Maroon">c<sub>1</sub></font></span>)</span> <a href="power.html#K3">to_power</a> 2
 <b>by </b><i><a class="ref" href="fib_num2.html#T4">FIB_NUM2:4</a></i>;<br/>


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