Distance Between Points

I need some help. I have to create a function that will calculate the distance between points (x1,y1) and (x2, y2). All numbers are of type double. I keep getting incorrect output. I am usinge visual studio and C language. Here is my code.

#include <stdio.h>
#include <math.h> 

double calculate_distance (double x1,double y1,double x2 ,double y2)

{

double distance;

double distance_x = x1-x2;

double distance_y = y1- y2; 

distance = sqrt( (distance_x * distance_x) + (distance_y * distance_y));

return distance;

}

int main ()
{
double x1;

double x2;

double y1;

double y2; 

printf ("Let me help you find the distance between two points (x1,y1) and (x2, y2)."); 

printf ("\n\nEnter coordinate for x1:");
scanf ("%f", &x1); 

printf ("\nEnter coordinate for y1:");
scanf ("%f", &y1); 

printf ("\nEnter coordinate for x2:");
scanf ("%f", &x2); 

printf ("\nEnter coordinate for y2:");
scanf ("%f", &y2); 

printf ("The distance between (%f,%f) and (%f,%f) is %.2f\n\n", x1,y1,x2,y2, calculate_distance(x1,y1,x2,y2)); 

return ;

}