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<a NAME="E1:10"/>
(  <a href="xxreal_0.html#K2">-infty</a>  <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K2">{</a><span class="default"><a href="xxreal_0.html#K2">-infty</a> ,<a href="xxreal_0.html#K1">+infty</a> </span><a href="tarski.html#K2">}</a></span> &amp;  <a href="xxreal_0.html#K1">+infty</a>  <a href="hidden.html#R2">in</a> <span class="p1"><a href="tarski.html#K2">{</a><span class="default"><a href="xxreal_0.html#K2">-infty</a> ,<a href="xxreal_0.html#K1">+infty</a> </span><a href="tarski.html#K2">}</a></span> )
 
<b>by </b><i><a class="ref" href="tarski.html#D2">TARSKI:def 2</a></i>;<br/>
<b>hence </b><a NAME="E2:10"/>
(  <a href="xxreal_0.html#K2">-infty</a>  is   <a href="supinf_1.html#NM3">R_eal</a> &amp;  <a href="xxreal_0.html#K1">+infty</a>  is   <a href="supinf_1.html#NM3">R_eal</a> )
 <b>by </b><i><a class="ref" href="xboole_0.html#D2">XBOOLE_0:def 2</a></i>;<br/>


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