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<b>let </b><font color="Maroon">A</font> be   <a href="cat_1.html#NM4">Category</a>;<br/><b>let </b><font color="Maroon">B</font> be   <a href="cat_1.html#NM4">Category</a>;<br/><b>let </b><font color="Maroon">F1</font> be    <a href="cat_1.html#M2">Functor</a> of <font color="Maroon">A</font>,<font color="Maroon">B</font>;<br/><b>let </b><font color="Maroon">F2</font> be    <a href="cat_1.html#M2">Functor</a> of <font color="Maroon">A</font>,<font color="Maroon">B</font>;<br/>







<b>assume </b><a NAME="E1:39"/><i><font color="Green">E7</font></i>: 
<font color="Maroon">F1</font> <a href="nattra_1.html#R2" target="_self">is_naturally_transformable_to</a> <font color="Maroon">F2</font>
 ;<br/>

<a NAME="E2:39"/><b>then </b><i><font color="Green">E8</font></i>: 
<font color="Maroon">F1</font> <a href="nattra_1.html#R1" target="_self">is_transformable_to</a> <font color="Maroon">F2</font>
 
<b>by </b><i/>;<br/>
<b>let </b><font color="Maroon">t</font> be    <a href="nattra_1.html#M2" target="_self">natural_transformation</a> of <font color="Maroon">F1</font>,<font color="Maroon">F2</font>;<br/>

<b>thus </b><span class="p1">(<span class="default"><a href="nattra_1.html#K7" target="_self">id</a> <font color="Maroon">F2</font></span>)</span> <a href="nattra_1.html#K8" target="_self">`*`</a> <font color="Maroon">t</font> = 
<span class="p1">(<span class="default"><a href="nattra_1.html#K7" target="_self">id</a> <font color="Maroon">F2</font></span>)</span> <a href="nattra_1.html#K6" target="_self">`*`</a> <font color="Maroon">t</font>
<b>by </b><i>, </i>
<br/>.= 
<font color="Maroon">t</font>
<b>by </b><i>, </i>
;<br/>

<b>thus </b><font color="Maroon">t</font> <a href="nattra_1.html#K8" target="_self">`*`</a> <span class="p1">(<span class="default"><a href="nattra_1.html#K7" target="_self">id</a> <font color="Maroon">F1</font></span>)</span> = 
<font color="Maroon">t</font> <a href="nattra_1.html#K6" target="_self">`*`</a> <span class="p1">(<span class="default"><a href="nattra_1.html#K7" target="_self">id</a> <font color="Maroon">F1</font></span>)</span>
<b>by </b><i>, </i>
<br/>.= 
<font color="Maroon">t</font>
<b>by </b><i>, </i>
;<br/>


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