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<b>let </b><font color="Maroon">c<sub>1</sub></font>, <font color="Maroon">c<sub>2</sub></font> be   <a href="nat_1.html#NM1">Nat</a>;<br/>



<b>assume </b><a NAME="E1:30"/><i><font color="Green">E23</font></i>: 
 <a href="hilbert2.html#K1" target="_self">prop</a> <font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R1">=</a>  <a href="hilbert2.html#K1" target="_self">prop</a> <font color="Maroon">c<sub>2</sub></font>
 ;<br/>

<a NAME="E2:30"/>
3 <a href="nat_1.html#K1">+</a> <font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R1">=</a> 3 <a href="nat_1.html#K1">+</a> <font color="Maroon">c<sub>2</sub></font>
 
<b>by </b><i><a class="txt" href="hilbert2.html#E1:30"><i><font color="Green">E23</font></i></a>, <a class="ref" href="group_7.html#T1">GROUP_7:1</a></i>;<br/>
<b>hence </b><a NAME="E3:30"/>
<font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>2</sub></font>
 ;<br/>


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