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<b>let </b><font color="Maroon" title="c1">a</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/>

<b>thus </b><a NAME="E1:16"/>
( <font color="Maroon" title="c1">a</font> is   <a href="zf_lang.html#NM2" title="ZF_LANG:NM.2">ZF-formula</a> implies <font color="Maroon" title="c1">a</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>  )
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="16_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:16_1"/>
<font color="Maroon" title="c1">a</font> is   <a href="zf_lang.html#NM2" title="ZF_LANG:NM.2">ZF-formula</a>
 ;<br/>

<a NAME="E2:16_1"/><b>then </b>
<font color="Maroon" title="c1">a</font> is    <a href="subset_1.html#M1" title="SUBSET_1:mode.1">Element</a> of  <a href="zf_lang.html#K9" title="ZF_LANG:func.9">WFF</a> 
 
<b>by </b><i><a class="ref" href="zf_lang.html#D9" target="_self" title="ZF_LANG:def.9">Def9</a></i>;<br/>
<b>hence </b><a NAME="E3:16_1"/>
<font color="Maroon" title="c1">a</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> 
 ;<br/>


</div><b>end;</b></div>

<b>assume </b><a NAME="E2:16"/>
<font color="Maroon" title="c1">a</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> 
 ;<br/>

<b>hence </b><a NAME="E3:16"/>
<font color="Maroon" title="c1">a</font> is   <a href="zf_lang.html#NM2" title="ZF_LANG:NM.2">ZF-formula</a>
 <b>by </b><i><a class="ref" href="zf_lang.html#D8" target="_self" title="ZF_LANG:def.8">Def8</a>, <a class="ref" href="zf_lang.html#D9" target="_self" title="ZF_LANG:def.9">Def9</a></i>;<br/>


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