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<A NAME=ATAN>

<TITLE>ATAN</TITLE></A>
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<B>ATAN</B> _ _ _  _ _ _  _ _ _  _ _ _ <B>operator</B><P>
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The <em>atan</em> operator returns the arctangent of its argument. 
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syntax: </H3>
<em>atan</em>(&lt;expression&gt;) or <em>atan</em> &lt;simple\_expression&gt; 
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&lt;expression&gt; may be any scalar REDUCE expression, not an array, matrix or 

vector expression. &lt;simple\_expression&gt; must be a single identifier or 
begin with a prefix operator name. 
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examples: </H3>
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atan(middle); 

  ATAN(MIDDLE) 


on rounded; 

atan 45; 

  1.54857776147 


off rounded; 

int(atan(x),x); 

                     2
  2*ATAN(X)*X - LOG(X  + 1)
  ------------------------- 
              2


df(atan(y**2),y); 

   2*Y
  -------
   4
  Y  + 1

</TT></PRE><P>A numeric value is not returned by <em>atan</em> unless the switch
 

<A HREF=r37_0330.html>rounded</A> is on and its argument evaluates to a number. 

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