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<b>let </b><font color="Maroon" title="c1">i</font> be    <a href="subset_1.html#M2" title="SUBSET_1:mode.2">Element</a> of  <a href="numbers.html#K5" title="NUMBERS:func.5">NAT</a> ;<br/>

<b>assume </b><a NAME="E1:44_1"/><i><font color="Green" title="E15">A3</font></i>: 
<font color="Maroon">F<sub>1</sub></font>() <a href="xxreal_0.html#R1" title="XXREAL_0:pred.1">&lt;=</a> <font color="Maroon" title="c1">i</font>
 ;<br/>

<b>defpred </b><font color="Maroon">S<sub>1</sub></font>[  <a href="nat_1.html#NM1" title="NAT_1:NM.1">Nat</a>] <b>means </b><font color="Maroon">P<sub>1</sub></font>[<font color="Maroon">F<sub>1</sub></font>() <a href="xcmplx_0.html#K2" title="XCMPLX_0:func.2">+</a> $1];<br/>
<a NAME="E2:44_1"/><i><font color="Green" title="E16">A4</font></i>: 
<font color="Maroon">S<sub>1</sub></font>[0]
 
<b>by </b><i><a class="txt" href="nat_1.html#E1:44"><i><font color="Green" title="E13">A1</font></i></a></i>;<br/>
<b>reconsider </b><font color="Maroon" title="c2">M</font> = <font color="Maroon">F<sub>1</sub></font>() as    <a href="subset_1.html#M2" title="SUBSET_1:mode.2">Element</a> of  <a href="numbers.html#K5" title="NUMBERS:func.5">NAT</a>  <b>by </b><i><a class="ref" href="ordinal1.html#D13" title="ORDINAL1:def.13">ORDINAL1:def 13</a></i>;<br/>
<div><i><font color="Green" title="E17">A5</font></i>: <a class="txt" onclick="hs2(this)" href="javascript:()" title="44_1_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon" title="c3">m</font> be    <a href="subset_1.html#M2" title="SUBSET_1:mode.2">Element</a> of  <a href="numbers.html#K5" title="NUMBERS:func.5">NAT</a> ;<br/><b>assume </b><a NAME="E1:44_1_1"/><i><font color="Green" title="E18">A6</font></i>: 
<font color="Maroon">S<sub>1</sub></font>[<font color="Maroon" title="c3">m</font>]
 ;<br/><a NAME="E2:44_1_1"/>
<font color="Maroon">F<sub>1</sub></font>() <a href="xxreal_0.html#R1" title="XXREAL_0:pred.1">&lt;=</a> <font color="Maroon">F<sub>1</sub></font>() <a href="xcmplx_0.html#K2" title="XCMPLX_0:func.2">+</a> <font color="Maroon" title="c3">m</font>
 <b>by </b><i><a class="ref" href="nat_1.html#T11" target="_self" title="NAT_1:th.11">Th11</a></i>;<br/><a NAME="E3:44_1_1"/><b>then </b>
<font color="Maroon">P<sub>1</sub></font>[<span class="p1">(<span class="default"><font color="Maroon" title="c2">M</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> <font color="Maroon" title="c3">m</font></span>)</span> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1]
 <b>by </b><i><a class="txt" href="nat_1.html#E2:44"><i><font color="Green" title="E14">A2</font></i></a>, <a class="txt" href="nat_1.html#E1:44_1_1"><i><font color="Green" title="E18">A6</font></i></a></i>;<br/><b>hence </b><a NAME="E4:44_1_1"/>
<font color="Maroon">S<sub>1</sub></font>[<font color="Maroon" title="c3">m</font> <a href="nat_1.html#K1" title="NAT_1:func.1">+</a> 1]
 ;<br/></div><b>end;</b></div>
<a NAME="E5:44_1"/><i><font color="Green" title="E18">A7</font></i>: 
for <font color="Olive" title="b1">m</font> being   <a href="subset_1.html#M2" title="SUBSET_1:mode.2">Element</a> of  <a href="numbers.html#K5" title="NUMBERS:func.5">NAT</a>  holds  <font color="Maroon">S<sub>1</sub></font>[<font color="Olive" title="b1">m</font>]
 
<b>from </b><i><a class="ref" href="nat_1.html#S1" target="_self" title="NAT_1:sch.1">NAT_1:sch 1</a>(<a class="txt" href="nat_1.html#E2:44_1"><i><font color="Green" title="E16">A4</font></i></a>, <a class="txt" href="nat_1.html#E4:44_1"><i><font color="Green" title="E17">A5</font></i></a>);<br/></i>
<b>consider </b><font color="Maroon" title="c3">m</font> being   <a href="nat_1.html#NM1" title="NAT_1:NM.1">Nat</a><b> such that </b><br/><a NAME="E7:44_1"/><i><font color="Green" title="E19">A8</font></i>: 
<font color="Maroon" title="c1">i</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon">F<sub>1</sub></font>() <a href="xcmplx_0.html#K2" title="XCMPLX_0:func.2">+</a> <font color="Maroon" title="c3">m</font>
 <b>by </b><i><a class="txt" href="nat_1.html#E1:44_1"><i><font color="Green" title="E15">A3</font></i></a>, <a class="ref" href="nat_1.html#T10" target="_self" title="NAT_1:th.10">Th10</a></i>;<br/>
<a NAME="E8:44_1"/>
<font color="Maroon" title="c3">m</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="numbers.html#K5" title="NUMBERS:func.5">NAT</a> 
 
<b>by </b><i><a class="ref" href="ordinal1.html#D13" title="ORDINAL1:def.13">ORDINAL1:def 13</a></i>;<br/>
<b>hence </b><a NAME="E9:44_1"/>
<font color="Maroon">P<sub>1</sub></font>[<font color="Maroon" title="c1">i</font>]
 <b>by </b><i><a class="txt" href="nat_1.html#E5:44_1"><i><font color="Green" title="E18">A7</font></i></a>, <a class="txt" href="nat_1.html#E7:44_1"><i><font color="Green" title="E19">A8</font></i></a></i>;<br/>


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