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atan (<valarray>)

Operates on the elements of an input valarray, returning a valarray whose elements are equal to the principal value of the arctangent of the elements of the input valarray.

template<class Type> 
   valarray<Type> atan( 
      const valarray<Type>& _Left 
   );

_Left

The input valarray whose elements are to be operated on by the member function.

A valarray whose elements are equal to the arctangent of the elements of the input valarray.

The units of the returned elements are in radians.

The return value is a principal value between +pi/2 and –pi/2 that is consistent with the tangent value input.

// valarray_atan.cpp
// compile with: /EHsc
#include <valarray>
#include <iostream>
#include <iomanip>

int main( )
{
   using namespace std;
   double pi = 3.14159265359;
   int i;

   valarray<double> va1 ( 9 );
   va1 [ 0 ] = -100;
   for ( i = 1 ; i < 8 ; i++ )
      va1 [ i ] =  5 * ( 0.25 * i - 1 );
   va1 [ 8 ] = 100;
   valarray<double> va2 ( 9 );

   cout << "The initial valarray is: ";
   for ( i = 0 ; i < 9 ; i++ )
      cout << va1 [ i ] << " ";
   cout << "." << endl;

   va2 = atan ( va1 );
   cout << "The arcsine of the initial valarray is:\n";
   for ( i = 0 ; i < 9 ; i++ )
      cout << setw(10) << va2 [ i ]
           << "  radians, which is  "
           << setw(11) << (180/pi) * va2 [ i ]
           << "  degrees" << endl;
   cout << endl;
}
The initial valarray is: -100 -3.75 -2.5 -1.25 0 1.25 2.5 3.75 100 .
The arcsine of the initial valarray is:
   -1.5608  radians, which is     -89.4271  degrees
  -1.31019  radians, which is     -75.0686  degrees
  -1.19029  radians, which is     -68.1986  degrees
 -0.896055  radians, which is     -51.3402  degrees
         0  radians, which is            0  degrees
  0.896055  radians, which is      51.3402  degrees
   1.19029  radians, which is      68.1986  degrees
   1.31019  radians, which is      75.0686  degrees
    1.5608  radians, which is      89.4271  degrees

Header: <valarray>

Namespace: std

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