arg

Extracts the argument from a complex number.

template<class Type>
   Type arg(
      const complex<Type>& _ComplexNum
   );

Parameters

• _ComplexNum
  The complex number whose argument is to be determined.

Return Value

The argument of the complex number.

Remarks

The argument is the angle that the complex vector makes with the positive real axis in the complex plane. For a complex number a + bi, the argument is equal to arctan(b/a). The angle has a positive sense when measured in a counterclockwise direction from the positive real axis and a negative sense when measured in a clockwise direction. The principal values are greater than –pi and less than or equal to +pi.

Example

// complex_arg.cpp
// compile with: /EHsc
#include <complex>
#include <iostream>

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

   // Complex numbers can be entered in polar form with
   // modulus and argument parameter inputs but are
   // stored in Cartesian form as real & imag coordinates
   complex <double> c1 ( polar ( 5.0 ) );   // Default argument = 0
   complex <double> c2 ( polar ( 5.0 , pi / 6 ) );
   complex <double> c3 ( polar ( 5.0 , 13 * pi / 6 ) );
   cout << "c1 = polar ( 5.0 ) = " << c1 << endl;
   cout << "c2 = polar ( 5.0 , pi / 6 ) = " << c2 << endl;
   cout << "c3 = polar ( 5.0 , 13 * pi / 6 ) = " << c3 << endl;

   // The modulus and argument of a complex number can be rcovered
   // using abs & arg member functions
   double absc1 = abs ( c1 );
   double argc1 = arg ( c1 );
   cout << "The modulus of c1 is recovered from c1 using: abs ( c1 ) = "
        << absc1 << endl;
   cout << "Argument of c1 is recovered from c1 using:\n arg ( c1 ) = "
        << argc1 << " radians, which is " << argc1 * 180 / pi
        << " degrees." << endl;

   double absc2 = abs ( c2 );
   double argc2 = arg ( c2 );
   cout << "The modulus of c2 is recovered from c2 using: abs ( c2 ) = "
        << absc2 << endl;
   cout << "Argument of c2 is recovered from c2 using:\n arg ( c2 ) = "
        << argc2 << " radians, which is " << argc2 * 180 / pi
        << " degrees." << endl;

   // Testing if the principal angles of c2 and c3 are the same
   if ( (arg ( c2 ) <= ( arg ( c3 ) + .00000001) ) || 
        (arg ( c2 ) >= ( arg ( c3 ) - .00000001) ) )
      cout << "The complex numbers c2 & c3 have the "
           << "same principal arguments."<< endl;
   else
      cout << "The complex numbers c2 & c3 don't have the "
           << "same principal arguments." << endl;
}

c1 = polar ( 5.0 ) = (5,0)
c2 = polar ( 5.0 , pi / 6 ) = (4.33013,2.5)
c3 = polar ( 5.0 , 13 * pi / 6 ) = (4.33013,2.5)
The modulus of c1 is recovered from c1 using: abs ( c1 ) = 5
Argument of c1 is recovered from c1 using:
 arg ( c1 ) = 0 radians, which is 0 degrees.
The modulus of c2 is recovered from c2 using: abs ( c2 ) = 5
Argument of c2 is recovered from c2 using:
 arg ( c2 ) = 0.523599 radians, which is 30 degrees.
The complex numbers c2 & c3 have the same principal arguments.

Requirements

Header: <complex>

Namespace: std

See Also

Other Resources

<complex> Members