Error message "1d returned 1 exit status" ？？？

#include<iostream>
#include<cmath>
using namespace std;

void polar_to_rect(double&, double&, double , double );

int main()                                           
{               
    char ch;                                         
    double mag, angle, x, y;
    
    
    cout<<"           This program converts  a polar vector to a rectangular vector.."<<endl<<endl;
    
    while (ch != 'n')
    {
          cout<<"Enter the value of mag: ";      
          cin>>mag;
          cout<<"Enter the value of angle: ";
          cin>>angle;
          
          
          polar_to_rect(mag,angle, x, y);
          cout<<"                            >>x = "<<x<<endl;
          cout<<"                            >>y= "<<y<<endl<<endl;
          cout<<"Another calculation? (y/n)... ";
          cin>>ch;
    }
    
    
    return 0;                                      
}  

void polar_to_rec(double _mag, double angle, double &x, double &y)
{     
      x = _mag * cos(angle);
	  y = _mag * sin(angle);
	  
      return;
}</cmath></iostream>