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<b>let </b><font color="Maroon">F1</font> be  <a href="functor0.html#V15">covariant</a>  <a href="functor0.html#M2">Functor</a> of <font color="Maroon">A</font>,<font color="Maroon">B</font>, <font color="Maroon">F2</font> be  <a href="functor0.html#V15">covariant</a>  <a href="functor0.html#M2">Functor</a> of <font color="Maroon">A</font>,<font color="Maroon">B</font>;<br/>

<b>assume </b><b>that </b><br/><a NAME="E1:49_1_2"/><i><font color="Green">E31</font></i>: 
<font color="Maroon">F1</font> <a href="functor2.html#R2">is_naturally_transformable_to</a> <font color="Maroon">F2</font>
 <b>and </b><br/><a NAME="E2:49_1_2"/><i><font color="Green">E32</font></i>: 
<font color="Maroon">F2</font> <a href="functor2.html#R1">is_transformable_to</a> <font color="Maroon">F1</font>
 ;<br/>

<b>given </b><font color="Maroon">t</font> being    <a href="functor2.html#M2">natural_transformation</a> of <font color="Maroon">F1</font>,<font color="Maroon">F2</font><b> such that </b><a NAME="E3:49_1_2"/><i><font color="Green">E33</font></i>: 
for <font color="Olive">a</font> being  <a href="altcat_1.html#NM1">object</a> of <font color="Maroon">A</font> holds  <font color="Maroon">t</font> <a href="functor2.html#K2">!</a> <font color="Olive">a</font> is <a href="altcat_3.html#V3">iso</a>
 ;<br/>

<b>thus </b><a NAME="E4:49_1_2"/>
<font color="Maroon">F2</font> <a href="functor2.html#R2">is_naturally_transformable_to</a> <font color="Maroon">F1</font>
 <b>by </b><i>, , , </i>;<br/>

<b>thus </b><a NAME="E5:49_1_2"/>
<font color="Maroon">F1</font> <a href="functor2.html#R1">is_transformable_to</a> <font color="Maroon">F2</font>
 <b>by </b><i>, <a class="ref" href="functor2.html#D6">FUNCTOR2:def 6</a></i>;<br/>

<b>consider </b><font color="Maroon">f</font> being    <a href="functor2.html#M2">natural_transformation</a> of <font color="Maroon">F2</font>,<font color="Maroon">F1</font><b> such that </b><br/><a NAME="E7:49_1_2"/><i><font color="Green">E34</font></i>: 
for <font color="Olive">a</font> being  <a href="altcat_1.html#NM1">object</a> of <font color="Maroon">A</font> holds <br/> ( <font color="Maroon">f</font> <a href="funct_1.html#K1">.</a> <font color="Olive">a</font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">t</font> <a href="functor2.html#K2">!</a> <font color="Olive">a</font></span>)</span> <a href="altcat_3.html#K1">"</a>  &amp; <font color="Maroon">f</font> <a href="functor2.html#K2">!</a> <font color="Olive">a</font> is <a href="altcat_3.html#V3">iso</a> )
 <b>by </b><i>, , , </i>;<br/>
<b>take </b>
<font color="Maroon">f</font>
;<br/>

<b>thus </b><a NAME="E8:49_1_2"/>
for <font color="Olive">a</font> being  <a href="altcat_1.html#NM1">object</a> of <font color="Maroon">A</font> holds  <font color="Maroon">f</font> <a href="functor2.html#K2">!</a> <font color="Olive">a</font> is <a href="altcat_3.html#V3">iso</a>
 <b>by </b><i/>;<br/>


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