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<b>let </b><font color="Maroon" title="c1">H1</font>, <font color="Maroon" title="c2">H2</font> be   <a href="zf_lang.html#NM2" title="ZF_LANG:NM.2">ZF-formula</a>;<br/>



<b>thus </b> <a href="zf_lang1.html#K3" title="ZF_LANG1:func.3">variables_in</a> <span class="p1">(<span class="default"><font color="Maroon" title="c1">H1</font> <a href="zf_lang.html#K11" title="ZF_LANG:func.11">=&gt;</a> <font color="Maroon" title="c2">H2</font></span>)</span> = 
 <a href="zf_lang1.html#K3" title="ZF_LANG1:func.3">variables_in</a> <span class="p1">(<span class="default"><font color="Maroon" title="c1">H1</font> <a href="zf_lang.html#K7" title="ZF_LANG:func.7">'&amp;'</a> <span class="p2">(<span class="default"><a href="zf_lang.html#K6" title="ZF_LANG:func.6">'not'</a> <font color="Maroon" title="c2">H2</font></span>)</span></span>)</span>
<b>by </b><i><a class="ref" href="zf_lang1.html#T153" target="_self" title="ZF_LANG1:th.153">Th153</a></i>
<br/>.= 
<span class="p1">(<span class="default"><a href="zf_lang1.html#K3" title="ZF_LANG1:func.3">variables_in</a> <font color="Maroon" title="c1">H1</font></span>)</span> <a href="xboole_0.html#K2" title="XBOOLE_0:func.2">\/</a> <span class="p1">(<span class="default"><a href="zf_lang1.html#K3" title="ZF_LANG1:func.3">variables_in</a> <span class="p2">(<span class="default"><a href="zf_lang.html#K6" title="ZF_LANG:func.6">'not'</a> <font color="Maroon" title="c2">H2</font></span>)</span></span>)</span>
<b>by </b><i><a class="ref" href="zf_lang1.html#T154" target="_self" title="ZF_LANG1:th.154">Th154</a></i>
<br/>.= 
<span class="p1">(<span class="default"><a href="zf_lang1.html#K3" title="ZF_LANG1:func.3">variables_in</a> <font color="Maroon" title="c1">H1</font></span>)</span> <a href="xboole_0.html#K2" title="XBOOLE_0:func.2">\/</a> <span class="p1">(<span class="default"><a href="zf_lang1.html#K3" title="ZF_LANG1:func.3">variables_in</a> <font color="Maroon" title="c2">H2</font></span>)</span>
<b>by </b><i><a class="ref" href="zf_lang1.html#T153" target="_self" title="ZF_LANG1:th.153">Th153</a></i>
;<br/>


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