/*-------------------------------------

     rect_pol.c -- 把直角坐标转换为极坐标

 -------------------------------------*/

 #include <stdio.h>

 #include <math.h>

 #define RAD_TO_DEG    (180 / (4 * atan(1.0)))

 typedef struct polar_v

 {

     double magnitude;

     double angle;

 } Polar_V;

 typedef struct rect_v

 {

     double x;

     double y;

 } Rect_V;

 Polar_V rect_to_polar(Rect_V);

 int main()

 {

     Rect_V input;

     Polar_V result;

     puts("Enter x and y coordinates; enter q to quit:");

     while (scanf("%lf %lf", &input.x, &input.y) == )

     {

         result = rect_to_polar(input);

         printf("magnitude = %0.2f, angle = %0.2f\n", result.magnitude, result.angle);

     }

     return ;

 }

 Polar_V rect_to_polar(Rect_V rv)

 {

     Polar_V pv;

     pv.magnitude = sqrt(pow(rv.x, ) + pow(rv.y, ));

     if (pv.magnitude == )

         pv.angle = ;

     else

         pv.angle = RAD_TO_DEG * atan2(rv.y, rv.x);

     return pv;

 }