text: atan (<valarray>)
  Visual Studio 2013
  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.
  // 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
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