<?xml version="1.0"?>
<div class="add">

<b>let </b><font color="Maroon" title="c1">C</font> be   <a href="cat_1.html#NM4" title="CAT_1:NM.4">Category</a>;<br/><b>let </b><font color="Maroon" title="c2">E</font> be    <a href="cat_2.html#M3" title="CAT_2:mode.3">Subcategory</a> of <font color="Maroon" title="c1">C</font>;<br/>



<b>set </b><font color="Maroon" title="c3">T</font> =  <a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font>;<br/>
<b>thus </b><a NAME="E1:28"/>
(  <a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font> is <a href="cat_1.html#V9" title="CAT_1:attr.9">full</a> implies for <font color="Olive" title="b1">a</font>, <font color="Olive" title="b2">b</font> being  <a href="cat_1.html#NM1" title="CAT_1:NM.1">Object</a> of <font color="Maroon" title="c2">E</font><br/> for <font color="Olive" title="b3">a'</font>, <font color="Olive" title="b4">b'</font> being  <a href="cat_1.html#NM1" title="CAT_1:NM.1">Object</a> of <font color="Maroon" title="c1">C</font>  st <font color="Olive" title="b1">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Olive" title="b3">a'</font> &amp; <font color="Olive" title="b2">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Olive" title="b4">b'</font> holds <br/> <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Olive" title="b1">a</font>,<font color="Olive" title="b2">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Olive" title="b3">a'</font>,<font color="Olive" title="b4">b'</font> )
 <div><a class="txt" onclick="hs2(this)" href="javascript:()" title="28_1"><b>proof </b></a><div class="add">

<b>assume </b><a NAME="E1:28_1"/><i><font color="Green" title="E16">A1</font></i>: 
for <font color="Olive" title="b1">a</font>, <font color="Olive" title="b2">b</font> being  <a href="cat_1.html#NM1" title="CAT_1:NM.1">Object</a> of <font color="Maroon" title="c2">E</font>  st  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Olive" title="b1">a</font></span>)</span>,<span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Olive" title="b2">b</font></span>)</span> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  holds <br/>for <font color="Olive" title="b3">g</font> being   <a href="cat_1.html#M1" title="CAT_1:mode.1">Morphism</a> of <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Olive" title="b1">a</font>,<span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Olive" title="b2">b</font> holds <br/> (  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Olive" title="b1">a</font>,<font color="Olive" title="b2">b</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  &amp;  ex <font color="Olive" title="b4">f</font> being   <a href="cat_1.html#M1" title="CAT_1:mode.1">Morphism</a> of <font color="Olive" title="b1">a</font>,<font color="Olive" title="b2">b</font> st <font color="Olive" title="b3">g</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Olive" title="b4">f</font> )
 ; <i><font color="Red">:: according to </font></i><a class="ref" href="cat_1.html#D23" title="CAT_1:def.23">CAT_1:def 23</a><br/>

<b>let </b><font color="Maroon" title="c4">a</font>, <font color="Maroon" title="c5">b</font> be   <a href="cat_1.html#NM1" title="CAT_1:NM.1">Object</a> of <font color="Maroon" title="c2">E</font>;<br/><b>let </b><font color="Maroon" title="c6">a'</font>, <font color="Maroon" title="c7">b'</font> be   <a href="cat_1.html#NM1" title="CAT_1:NM.1">Object</a> of <font color="Maroon" title="c1">C</font>;<br/>



<b>assume </b><a NAME="E2:28_1"/><i><font color="Green" title="E17">A2</font></i>: 
( <font color="Maroon" title="c4">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c6">a'</font> &amp; <font color="Maroon" title="c5">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c7">b'</font> )
 ;<br/>

<div><a class="txt" onclick="hs2(this)" href="javascript:()" title="28_1_1"><b>now </b></a><div class="add"><b>let </b><font color="Maroon" title="c8">x</font> be    <a href="hidden.html#M1" title="HIDDEN:mode.1">set</a> ;<br/><a NAME="E1:28_1_1"/>
 <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font> <a href="tarski.html#R1" title="TARSKI:pred.1">c=</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c6">a'</font>,<font color="Maroon" title="c7">b'</font>
 <b>by </b><i><a class="txt" href="cat_2.html#E2:28_1"><i><font color="Green" title="E17">A2</font></i></a>, <a class="ref" href="cat_2.html#D4" target="_self" title="CAT_2:def.4">Def4</a></i>;<br/><b>hence </b><a NAME="E2:28_1_1"/>
( <font color="Maroon" title="c8">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font> implies <font color="Maroon" title="c8">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c6">a'</font>,<font color="Maroon" title="c7">b'</font> )
 ;<br/><a NAME="E3:28_1_1"/><i><font color="Green" title="E18">A3</font></i>: 
( <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c4">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c6">a'</font> &amp; <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c5">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c7">b'</font> )
 <b>by </b><i><a class="txt" href="cat_2.html#E2:28_1"><i><font color="Green" title="E17">A2</font></i></a>, <a class="ref" href="cat_2.html#T22" target="_self" title="CAT_2:th.22">Th22</a></i>;<br/><b>assume </b><a NAME="E4:28_1_1"/><i><font color="Green" title="E19">A4</font></i>: 
<font color="Maroon" title="c8">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c6">a'</font>,<font color="Maroon" title="c7">b'</font>
 ;<br/><b>then reconsider </b><font color="Maroon" title="c9">g</font> = <font color="Maroon" title="c8">x</font> as    <a href="cat_1.html#M1" title="CAT_1:mode.1">Morphism</a> of <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c4">a</font>,<span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c5">b</font> <b>by </b><i><a class="txt" href="cat_2.html#E3:28_1_1"><i><font color="Green" title="E18">A3</font></i></a>, <a class="ref" href="cat_1.html#D7" title="CAT_1:def.7">CAT_1:def 7</a></i>;<br/><b>consider </b><font color="Maroon" title="c10">f</font> being    <a href="cat_1.html#M1" title="CAT_1:mode.1">Morphism</a> of <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font><b> such that </b><br/><a NAME="E7:28_1_1"/><i><font color="Green" title="E20">A5</font></i>: 
<font color="Maroon" title="c9">g</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c10">f</font>
 <b>by </b><i><a class="txt" href="cat_2.html#E1:28_1"><i><font color="Green" title="E16">A1</font></i></a>, <a class="txt" href="cat_2.html#E3:28_1_1"><i><font color="Green" title="E18">A3</font></i></a>, <a class="txt" href="cat_2.html#E4:28_1_1"><i><font color="Green" title="E19">A4</font></i></a></i>;<br/><a NAME="E8:28_1_1"/>
( <font color="Maroon" title="c9">g</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Maroon" title="c10">f</font> &amp;  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a>  )
 <b>by </b><i><a class="txt" href="cat_2.html#E1:28_1"><i><font color="Green" title="E16">A1</font></i></a>, <a class="txt" href="cat_2.html#E3:28_1_1"><i><font color="Green" title="E18">A3</font></i></a>, <a class="txt" href="cat_2.html#E4:28_1_1"><i><font color="Green" title="E19">A4</font></i></a>, <a class="txt" href="cat_2.html#E7:28_1_1"><i><font color="Green" title="E20">A5</font></i></a>, <a class="ref" href="funct_1.html#T35" title="FUNCT_1:th.35">FUNCT_1:35</a></i>;<br/><b>hence </b><a NAME="E9:28_1_1"/>
<font color="Maroon" title="c8">x</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font>
 <b>by </b><i><a class="ref" href="cat_1.html#D7" title="CAT_1:def.7">CAT_1:def 7</a></i>;<br/></div><b>end;</b></div>
<b>hence </b><a NAME="E4:28_1"/>
 <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c6">a'</font>,<font color="Maroon" title="c7">b'</font>
 <b>by </b><i><a class="ref" href="tarski.html#T2" title="TARSKI:th.2">TARSKI:2</a></i>;<br/>


</div><b>end;</b></div>

<b>assume </b><a NAME="E2:28"/><i><font color="Green" title="E16">A6</font></i>: 
for <font color="Olive" title="b1">a</font>, <font color="Olive" title="b2">b</font> being  <a href="cat_1.html#NM1" title="CAT_1:NM.1">Object</a> of <font color="Maroon" title="c2">E</font><br/> for <font color="Olive" title="b3">a'</font>, <font color="Olive" title="b4">b'</font> being  <a href="cat_1.html#NM1" title="CAT_1:NM.1">Object</a> of <font color="Maroon" title="c1">C</font>  st <font color="Olive" title="b1">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Olive" title="b3">a'</font> &amp; <font color="Olive" title="b2">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <font color="Olive" title="b4">b'</font> holds <br/> <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Olive" title="b1">a</font>,<font color="Olive" title="b2">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Olive" title="b3">a'</font>,<font color="Olive" title="b4">b'</font>
 ;<br/>

<b>let </b><font color="Maroon" title="c4">a</font>, <font color="Maroon" title="c5">b</font> be   <a href="cat_1.html#NM1" title="CAT_1:NM.1">Object</a> of <font color="Maroon" title="c2">E</font>; <i><font color="Red">:: according to </font></i><a class="ref" href="cat_1.html#D23" title="CAT_1:def.23">CAT_1:def 23</a><br/>

<b>assume </b><a NAME="E3:28"/><i><font color="Green" title="E17">A7</font></i>: 
 <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c4">a</font></span>)</span>,<span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c5">b</font></span>)</span> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
 ;<br/>

<b>let </b><font color="Maroon" title="c6">g</font> be    <a href="cat_1.html#M1" title="CAT_1:mode.1">Morphism</a> of <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c4">a</font>,<span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c5">b</font>;<br/>

<a NAME="E4:28"/><i><font color="Green" title="E18">A8</font></i>: 
( <font color="Maroon" title="c4">a</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c4">a</font> &amp; <font color="Maroon" title="c5">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c5">b</font> )
 
<b>by </b><i><a class="ref" href="cat_2.html#T22" target="_self" title="CAT_2:th.22">Th22</a></i>;<br/>
<a NAME="E5:28"/><b>then </b><i><font color="Green" title="E19">A9</font></i>: 
 <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c4">a</font></span>)</span>,<span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c5">b</font></span>)</span>
 
<b>by </b><i><a class="txt" href="cat_2.html#E2:28"><i><font color="Green" title="E16">A6</font></i></a></i>;<br/>
<b>thus </b><a NAME="E6:28"/>
 <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font> <a href="hidden.html#NR2" title="HIDDEN:NR.2">&lt;&gt;</a>  <a href="xboole_0.html#K1" title="XBOOLE_0:func.1">{}</a> 
 <b>by </b><i><a class="txt" href="cat_2.html#E2:28"><i><font color="Green" title="E16">A6</font></i></a>, <a class="txt" href="cat_2.html#E3:28"><i><font color="Green" title="E17">A7</font></i></a>, <a class="txt" href="cat_2.html#E4:28"><i><font color="Green" title="E18">A8</font></i></a></i>;<br/>

<a NAME="E7:28"/>
<font color="Maroon" title="c6">g</font> <a href="hidden.html#R2" title="HIDDEN:pred.2">in</a>  <a href="cat_1.html#K6" title="CAT_1:func.6">Hom</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c4">a</font></span>)</span>,<span class="p1">(<span class="default"><span class="p2">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="cat_1.html#K13" title="CAT_1:func.13">.</a> <font color="Maroon" title="c5">b</font></span>)</span>
 
<b>by </b><i><a class="txt" href="cat_2.html#E3:28"><i><font color="Green" title="E17">A7</font></i></a>, <a class="ref" href="cat_1.html#D7" title="CAT_1:def.7">CAT_1:def 7</a></i>;<br/>
<b>then reconsider </b><font color="Maroon" title="c7">f</font> = <font color="Maroon" title="c6">g</font> as    <a href="cat_1.html#M1" title="CAT_1:mode.1">Morphism</a> of <font color="Maroon" title="c4">a</font>,<font color="Maroon" title="c5">b</font> <b>by </b><i><a class="txt" href="cat_2.html#E5:28"><i><font color="Green" title="E19">A9</font></i></a>, <a class="ref" href="cat_1.html#D7" title="CAT_1:def.7">CAT_1:def 7</a></i>;<br/>
<b>take </b>
<font color="Maroon" title="c7">f</font>
;<br/>

<b>thus </b><a NAME="E9:28"/>
<font color="Maroon" title="c6">g</font> <a href="hidden.html#R1" title="HIDDEN:pred.1">=</a> <span class="p1">(<span class="default"><a href="cat_2.html#K8" title="CAT_2:func.8">incl</a> <font color="Maroon" title="c2">E</font></span>)</span> <a href="funct_2.html#K3" title="FUNCT_2:func.3">.</a> <font color="Maroon" title="c7">f</font>
 <b>by </b><i><a class="ref" href="funct_1.html#T35" title="FUNCT_1:th.35">FUNCT_1:35</a></i>;<br/>


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