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<b>let </b><font color="Maroon" title="c1">H</font> be   <a href="zf_lang.html#NM2" title="ZF_LANG:NM.2">ZF-formula</a>;<br/>

<b>assume </b><a NAME="E1:26"/>
<font color="Maroon" title="c1">H</font> is <a href="zf_lang.html#V10" title="ZF_LANG:attr.10">biconditional</a>
 ;<br/>

<a NAME="E2:26"/><b>then </b><i><font color="Green" title="E10">A1</font></i>: 
<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#K27" title="ZF_LANG:func.27">the_left_side_of</a> <font color="Maroon" title="c1">H</font></span>)</span> <a href="zf_lang.html#K12" title="ZF_LANG:func.12">&lt;=&gt;</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K28" title="ZF_LANG:func.28">the_right_side_of</a> <font color="Maroon" title="c1">H</font></span>)</span>
 
<b>by </b><i><a class="ref" href="zf_lang.html#T67" title="ZF_LANG:th.67">ZF_LANG:67</a></i>;<br/>
<b>hence </b><a NAME="E3:26"/>
<font color="Maroon" title="c1">H</font> is <a href="zf_lang.html#V5" title="ZF_LANG:attr.5">conjunctive</a>
 <b>by </b><i><a class="ref" href="zf_lang.html#T16" title="ZF_LANG:th.16">ZF_LANG:16</a></i>;<br/>

<a NAME="E4:26"/>
(  <a href="zf_lang.html#K21" title="ZF_LANG:func.21">the_left_argument_of</a> <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#K27" title="ZF_LANG:func.27">the_left_side_of</a> <font color="Maroon" title="c1">H</font></span>)</span> <a href="zf_lang.html#K11" title="ZF_LANG:func.11">=&gt;</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K28" title="ZF_LANG:func.28">the_right_side_of</a> <font color="Maroon" title="c1">H</font></span>)</span> &amp;  <a href="zf_lang.html#K22" title="ZF_LANG:func.22">the_right_argument_of</a> <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#K28" title="ZF_LANG:func.28">the_right_side_of</a> <font color="Maroon" title="c1">H</font></span>)</span> <a href="zf_lang.html#K11" title="ZF_LANG:func.11">=&gt;</a> <span class="p1">(<span class="default"><a href="zf_lang.html#K27" title="ZF_LANG:func.27">the_left_side_of</a> <font color="Maroon" title="c1">H</font></span>)</span> )
 
<b>by </b><i><a class="txt" href="zf_lang1.html#E2:26"><i><font color="Green" title="E10">A1</font></i></a>, <a class="ref" href="zf_lang1.html#T4" target="_self" title="ZF_LANG1:th.4">Th4</a></i>;<br/>
<b>hence </b><a NAME="E5:26"/>
(  <a href="zf_lang.html#K21" title="ZF_LANG:func.21">the_left_argument_of</a> <font color="Maroon" title="c1">H</font> is <a href="zf_lang.html#V9" title="ZF_LANG:attr.9">conditional</a> &amp;  <a href="zf_lang.html#K22" title="ZF_LANG:func.22">the_right_argument_of</a> <font color="Maroon" title="c1">H</font> is <a href="zf_lang.html#V9" title="ZF_LANG:attr.9">conditional</a> )
 <b>by </b><i><a class="ref" href="zf_lang.html#T22" title="ZF_LANG:th.22">ZF_LANG:22</a></i>;<br/>


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