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<b>let </b><font color="Maroon">c<sub>3</sub></font> be   <a href="cat_1.html#NM4">Category</a>;<br/>

<a NAME="E1:18_1_1"/>
 <a href="cat_1.html#K15">id</a> <font color="Maroon">c<sub>3</sub></font> <a href="isocat_1.html#NR1" target="_self">is_an_isomorphism</a> 
 
<b>by </b><i><a class="ref" href="cat_1.html#T122">CAT_1:122</a></i>;<br/>
<b>hence </b><a NAME="E2:18_1_1"/>
ex <font color="Olive">b<sub>1</sub></font> being   <a href="cat_1.html#M2">Functor</a> of <font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>3</sub></font> st <font color="Olive">b<sub>1</sub></font> <a href="isocat_1.html#NR1" target="_self">is_an_isomorphism</a> 
 ;<br/>


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