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<b>let </b><font color="Maroon">c<sub>1</sub></font> be   <a href="bhsp_1.html#NM1">RealUnitarySpace</a>;<br/><b>let </b><font color="Maroon">c<sub>2</sub></font> be   <a href="rlvect_1.html#NM1">VECTOR</a> of <font color="Maroon">c<sub>1</sub></font>;<br/><b>let </b><font color="Maroon">c<sub>3</sub></font>, <font color="Maroon">c<sub>4</sub></font> be    <a href="rusub_1.html#M1">Subspace</a> of <font color="Maroon">c<sub>1</sub></font>;<br/>





<b>assume </b><a NAME="E1:66"/><i><font color="Green">E51</font></i>: 
<font color="Maroon">c<sub>1</sub></font> <a href="rusub_2.html#R1" target="_self">is_the_direct_sum_of</a> <font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font>
 ;<br/>

<a NAME="E2:66"/><b>then </b><i><font color="Green">E52</font></i>: 
( <font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span>)</span> <a href="domain_1.html#K2">`1</a> </span>)</span> <a href="rlvect_1.html#K4">+</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span>)</span> <a href="domain_1.html#K3">`2</a> </span>)</span> &amp; <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span>)</span> <a href="domain_1.html#K2">`1</a>  <a href="rlvect_1.html#R1">in</a> <font color="Maroon">c<sub>3</sub></font> &amp; <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span>)</span> <a href="domain_1.html#K3">`2</a>  <a href="rlvect_1.html#R1">in</a> <font color="Maroon">c<sub>4</sub></font> )
 
<b>by </b><i><a class="ref" href="rusub_2.html#D6" target="_self">Def6</a></i>;<br/>
<a NAME="E3:66"/><i><font color="Green">E53</font></i>: 
<font color="Maroon">c<sub>1</sub></font> <a href="rusub_2.html#R1" target="_self">is_the_direct_sum_of</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>3</sub></font>
 
<b>by </b><i><a class="txt" href="rusub_2.html#E1:66"><i><font color="Green">E51</font></i></a>, <a class="txt" href="rusub_2.html#E53"><i><font color="Green">Lemma39</font></i></a></i>;<br/>
<a NAME="E4:66"/><b>then </b><i><font color="Green">E54</font></i>: 
<font color="Maroon">c<sub>2</sub></font> <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="domain_1.html#K3">`2</a> </span>)</span> <a href="rlvect_1.html#K4">+</a> <span class="p1">(<span class="default"><span class="p2">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="domain_1.html#K2">`1</a> </span>)</span>
 
<b>by </b><i><a class="ref" href="rusub_2.html#D6" target="_self">Def6</a></i>;<br/>
<a NAME="E5:66"/>
( <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="domain_1.html#K2">`1</a>  <a href="rlvect_1.html#R1">in</a> <font color="Maroon">c<sub>4</sub></font> &amp; <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="domain_1.html#K3">`2</a>  <a href="rlvect_1.html#R1">in</a> <font color="Maroon">c<sub>3</sub></font> )
 
<b>by </b><i><a class="txt" href="rusub_2.html#E3:66"><i><font color="Green">E53</font></i></a>, <a class="ref" href="rusub_2.html#D6" target="_self">Def6</a></i>;<br/>
<b>hence </b><a NAME="E6:66"/>
<span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>3</sub></font>,<font color="Maroon">c<sub>4</sub></font></span>)</span> <a href="domain_1.html#K2">`1</a>  <a href="hidden.html#R1">=</a> <span class="p1">(<span class="default"><font color="Maroon">c<sub>2</sub></font> <a href="rusub_2.html#K4" target="_self">|--</a> <font color="Maroon">c<sub>4</sub></font>,<font color="Maroon">c<sub>3</sub></font></span>)</span> <a href="domain_1.html#K3">`2</a> 
 <b>by </b><i><a class="txt" href="rusub_2.html#E1:66"><i><font color="Green">E51</font></i></a>, <a class="txt" href="rusub_2.html#E2:66"><i><font color="Green">E52</font></i></a>, <a class="txt" href="rusub_2.html#E4:66"><i><font color="Green">E54</font></i></a>, <a class="ref" href="rusub_2.html#T45" target="_self">Th45</a></i>;<br/>


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