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<a NAME="E1:4_1_1"/>
 <a href="zfrefle1.html#K1" title="ZFREFLE1:func.1">ZF-axioms</a>  <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="zf_lang.html#K9" title="ZF_LANG:func.9">WFF</a> 
 
<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="4_1_1_1"><span class="kw">proof </span></a><div class="add">

<span class="kw">let </span><font color="Maroon" title="c1">e</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ; <span class="comment"><font color="firebrick">:: according to </font></span><a class="ref" href="tarski.html#D3" title="TARSKI:def.3">TARSKI:def 3</a> <a class="txt" onclick="hs(this)" href="javascript:()"><span class="comment"><font color="firebrick">::  thesis: </font></span></a><span class="hide"> (  not <font color="Maroon" title="c1">e</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="zfrefle1.html#K1" title="ZFREFLE1:func.1">ZF-axioms</a>  or <font color="Maroon" title="c1">e</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="zf_lang.html#K9" title="ZF_LANG:func.9">WFF</a>  )</span><br/>

<span class="kw">thus </span><a NAME="E1:4_1_1_1"/>
(  not <font color="Maroon" title="c1">e</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="zfrefle1.html#K1" title="ZFREFLE1:func.1">ZF-axioms</a>  or <font color="Maroon" title="c1">e</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="zf_lang.html#K9" title="ZF_LANG:func.9">WFF</a>  )
 <span class="kw">by</span> <span class="lab"><a class="ref" href="zfrefle1.html#D4" target="_self" title="ZFREFLE1:def.4">Def4</a></span>; <a class="txt" onclick="hs(this)" href="javascript:()"><span class="comment"><font color="firebrick">::  thesis: </font></span></a><span class="hide"> verum</span><br/>


</div><span class="kw">end;</span></div>
<span class="kw">hence </span><a NAME="E2:4_1_1"/>
 <a href="zfrefle1.html#K1" title="ZFREFLE1:func.1">ZF-axioms</a>  is   <a href="subset_1.html#NM2" title="SUBSET_1:NM.2">Subset</a> of <a href="zf_lang.html#K9" title="ZF_LANG:func.9">WFF</a>
 ; <a class="txt" onclick="hs(this)" href="javascript:()"><span class="comment"><font color="firebrick">::  thesis: </font></span></a><span class="hide"> verum</span><br/>


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