怎么求下面的图片上的函数初始化

 #include <complex>
#include <iostream>

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

   // The first constructor specifies real & imaginary parts
   complex <double> c1 ( 4.0 , 5.0 );
   cout << "Specifying initial real & imaginary parts,"
        << "c1 = " << c1 << endl; 

   // The second constructor initializes values of the real &
   // imaginary parts using those of another complex number
   complex <double> c2 ( c1 );
   cout << "Initializing with the real and imaginary parts of c1,"
        << " c2 = " << c2 << endl; 

   // Complex numbers can be initialized in polar form
   // but will be stored in Cartesian form
   complex <double> c3 ( polar ( sqrt( (double)8 ) , pi / 4 ) );
   cout << "c3 = polar ( sqrt ( 8 ) , pi / 4 ) = " << c3 << endl; 

   // The modulus and argument of a complex number can be recovered
   double absc3 = abs ( c3 );
   double argc3 = arg ( c3 );
   cout << "The modulus of c3 is recovered from c3 using: abs ( c3 ) = "
        << absc3 << endl;
   cout << "Argument of c3 is recovered from c3 using:\n arg ( c3 ) = "
        << argc3 << " radians, which is " << argc3 * 180 / pi
        << " degrees." << endl;
}