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<b>let </b><font color="Maroon" title="c1">H</font>, <font color="Maroon" title="c2">F</font> be   <a href="zf_lang.html#NM2" title="ZF_LANG:NM.2">ZF-formula</a>; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> ( <font color="Maroon" title="c1">H</font> is <a href="zf_lang.html#V7" title="ZF_LANG:attr.7">atomic</a> implies  not <font color="Maroon" title="c2">F</font> <a href="zf_lang.html#R3" title="ZF_LANG:pred.3">is_proper_subformula_of</a> <font color="Maroon" title="c1">H</font> )</span><br/>



<b>assume </b><a NAME="E1:91"/>
<font color="Maroon" title="c1">H</font> is <a href="zf_lang.html#V7" title="ZF_LANG:attr.7">atomic</a>
 ; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> not <font color="Maroon" title="c2">F</font> <a href="zf_lang.html#R3" title="ZF_LANG:pred.3">is_proper_subformula_of</a> <font color="Maroon" title="c1">H</font></span><br/>

<a NAME="E2:91"/><b>then </b>
( <font color="Maroon" title="c1">H</font> <a href="zf_lang.html#NR1" title="ZF_LANG:NR.1">is_equality</a>  or <font color="Maroon" title="c1">H</font> <a href="zf_lang.html#NR2" title="ZF_LANG:NR.2">is_membership</a>  )
 
<b>by </b><i><a class="ref" href="zf_lang.html#D15" target="_self" title="ZF_LANG:def.15">Def15</a></i>;<br/>
<a NAME="E3:91"/><b>then </b>
( <font color="Maroon" title="c1">H</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K18" title="ZF_LANG:func.18">Var1</a> <font color="Maroon" title="c1">H</font></span>)</span> <a href="zf_lang.html#K4" title="ZF_LANG:func.4">'='</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K19" title="ZF_LANG:func.19">Var2</a> <font color="Maroon" title="c1">H</font></span>)</span> or <font color="Maroon" title="c1">H</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K18" title="ZF_LANG:func.18">Var1</a> <font color="Maroon" title="c1">H</font></span>)</span> <a href="zf_lang.html#K5" title="ZF_LANG:func.5">'in'</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K19" title="ZF_LANG:func.19">Var2</a> <font color="Maroon" title="c1">H</font></span>)</span> )
 
<b>by </b><i><a class="ref" href="zf_lang.html#T53" target="_self" title="ZF_LANG:th.53">Th53</a>, <a class="ref" href="zf_lang.html#T54" target="_self" title="ZF_LANG:th.54">Th54</a></i>;<br/>
<b>hence </b><a NAME="E4:91"/>
not <font color="Maroon" title="c2">F</font> <a href="zf_lang.html#R3" title="ZF_LANG:pred.3">is_proper_subformula_of</a> <font color="Maroon" title="c1">H</font>
 <b>by </b><i><a class="ref" href="zf_lang.html#T88" target="_self" title="ZF_LANG:th.88">Th88</a>, <a class="ref" href="zf_lang.html#T89" target="_self" title="ZF_LANG:th.89">Th89</a></i>; <a class="txt" onclick="hs(this)" href="javascript:()"><i><font color="Red">::  thesis: </font></i></a><span class="hide"> verum</span><br/>


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