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<b>let </b><font color="Maroon">x1</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">x2</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">x3</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">x4</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">x5</font> be    <a href="hidden.html#M1">set</a> ;<br/><b>let </b><font color="Maroon">x6</font> be    <a href="hidden.html#M1">set</a> ;<br/>











<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="20_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon">x</font> be    <a href="hidden.html#M1">set</a> ;<br/><a NAME="E1:20_1"/>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="enumset1.html#K4" target="_self">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font>,<font color="Maroon">x3</font>,<font color="Maroon">x4</font>,<font color="Maroon">x5</font>,<font color="Maroon">x6</font></span><a href="enumset1.html#K4" target="_self">}</a></span> iff ( <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x1</font> or <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x2</font> or <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x3</font> or <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x4</font> or <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x5</font> or <font color="Maroon">x</font> <a href="hidden.html#R1">=</a> <font color="Maroon">x6</font> ) )
 <b>by </b><i/>;<br/><a NAME="E2:20_1"/><b>then </b>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="enumset1.html#K4" target="_self">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font>,<font color="Maroon">x3</font>,<font color="Maroon">x4</font>,<font color="Maroon">x5</font>,<font color="Maroon">x6</font></span><a href="enumset1.html#K4" target="_self">}</a></span> iff ( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="enumset1.html#K1" target="_self">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font>,<font color="Maroon">x3</font></span><a href="enumset1.html#K1" target="_self">}</a></span> or <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="enumset1.html#K1" target="_self">{</a><span class="default"><font color="Maroon">x4</font>,<font color="Maroon">x5</font>,<font color="Maroon">x6</font></span><a href="enumset1.html#K1" target="_self">}</a></span> ) )
 <b>by </b><i/>;<br/><b>hence </b><a NAME="E3:20_1"/>
( <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="enumset1.html#K4" target="_self">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font>,<font color="Maroon">x3</font>,<font color="Maroon">x4</font>,<font color="Maroon">x5</font>,<font color="Maroon">x6</font></span><a href="enumset1.html#K4" target="_self">}</a></span> iff <font color="Maroon">x</font> <a href="hidden.html#R2">in</a> <span class="p1"><a href="enumset1.html#K1" target="_self">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font>,<font color="Maroon">x3</font></span><a href="enumset1.html#K1" target="_self">}</a></span> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="enumset1.html#K1" target="_self">{</a><span class="default"><font color="Maroon">x4</font>,<font color="Maroon">x5</font>,<font color="Maroon">x6</font></span><a href="enumset1.html#K1" target="_self">}</a></span> )
 <b>by </b><i><a class="ref" href="xboole_0.html#D2">XBOOLE_0:def 2</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E2:20"/>
<span class="p1"><a href="enumset1.html#K4" target="_self">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font>,<font color="Maroon">x3</font>,<font color="Maroon">x4</font>,<font color="Maroon">x5</font>,<font color="Maroon">x6</font></span><a href="enumset1.html#K4" target="_self">}</a></span> <a href="hidden.html#R1">=</a> <span class="p1"><a href="enumset1.html#K1" target="_self">{</a><span class="default"><font color="Maroon">x1</font>,<font color="Maroon">x2</font>,<font color="Maroon">x3</font></span><a href="enumset1.html#K1" target="_self">}</a></span> <a href="xboole_0.html#K2">\/</a> <span class="p1"><a href="enumset1.html#K1" target="_self">{</a><span class="default"><font color="Maroon">x4</font>,<font color="Maroon">x5</font>,<font color="Maroon">x6</font></span><a href="enumset1.html#K1" target="_self">}</a></span>
 <b>by </b><i><a class="ref" href="tarski.html#T2">TARSKI:2</a></i>;<br/>


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