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<b>let </b><font color="Maroon">c<sub>1</sub></font>, <font color="Maroon">c<sub>2</sub></font>, <font color="Maroon">c<sub>3</sub></font>, <font color="Maroon">c<sub>4</sub></font> be    <a href="hidden.html#M1">set</a> ;<br/>

<a NAME="E1:139"/><i><font color="Green">E80</font></i>: 
( <font color="Maroon">c<sub>3</sub></font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">c<sub>4</sub></font> <a href="tarski.html#R1">c=</a> <font color="Maroon">c<sub>1</sub></font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">c<sub>2</sub></font> iff ( <font color="Maroon">c<sub>3</sub></font> <a href="tarski.html#R1">c=</a> <font color="Maroon">c<sub>1</sub></font> &amp; <font color="Maroon">c<sub>4</sub></font> <a href="tarski.html#R1">c=</a> <font color="Maroon">c<sub>2</sub></font> ) )
 
<b>by </b><i><a class="ref" href="cohsp_1.html#T79" target="_self">Th79</a></i>;<br/>
<a NAME="E2:139"/>
( <font color="Maroon">c<sub>1</sub></font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">c<sub>2</sub></font> <a href="tarski.html#R1">c=</a> <font color="Maroon">c<sub>3</sub></font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">c<sub>4</sub></font> iff ( <font color="Maroon">c<sub>1</sub></font> <a href="tarski.html#R1">c=</a> <font color="Maroon">c<sub>3</sub></font> &amp; <font color="Maroon">c<sub>2</sub></font> <a href="tarski.html#R1">c=</a> <font color="Maroon">c<sub>4</sub></font> ) )
 
<b>by </b><i><a class="ref" href="cohsp_1.html#T79" target="_self">Th79</a></i>;<br/>
<b>hence </b><a NAME="E3:139"/>
( <font color="Maroon">c<sub>1</sub></font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>3</sub></font> <a href="cohsp_1.html#K14" target="_self">U+</a> <font color="Maroon">c<sub>4</sub></font> iff ( <font color="Maroon">c<sub>1</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>3</sub></font> &amp; <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R1">=</a> <font color="Maroon">c<sub>4</sub></font> ) )
 <b>by </b><i><a class="txt" href="cohsp_1.html#E1:139"><i><font color="Green">E80</font></i></a>, <a class="ref" href="xboole_0.html#D10">XBOOLE_0:def 10</a></i>;<br/>


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