What am i doing wrong with my scope calculation function

Question

I i have this assignment and i just dont know what to do right now it does not give the the scope i need for every like 3 points its gives me some huge number.

here is the assignment

Write a program that accepts a polygon with n vertices, and calculates its perimeter. To perform the task against, two new types are required:

• The point structure contains the fields: Two integers indicating a reference point (coordinate) in the plane.
• The polygon structure contains the fields: A pointer to an array of type point, the size of the array, and the perimeter of the polygon.

A structure of type must be declared at the beginning of the program polygon, and make an input of n points.

There is no need to sort the points, it will be assumed that order The reception of the points is continuously, so that between every 2 adjacent points there is a side belonging to the polygon.

Below is the list of functions required to perform the task:

1. scanPoint
2. createPolygon
3. distance
4. calculateScope
5. addPoint
6. removePoint
7. freeMemory

Note: it must be assumed that the perimeter of a polygon with less than 3 vertices is equal to 0

  typedef struct point
  {
      int x, y;
   }point;
   
   typedef struct polygon
   {
      int n;
      point* points;
      double scope;
   }polygon;

and here is the code i tried to make

int main()
{
    int i, n, idx=0;
    polygon* poly;
    printf("Start Program\n");
    poly = createPolygon();
    printf("How many points to add: ");
    scanf_s("%d",&n);
    for (i = 0; i < n; i++)
    {
        printf("Point #%d: \n", i + 1);
        addPoint(poly);
    }
    printf("Output: Scope of polygon: %.2lf\n", poly->scope);
}


void scanPoint(point* p)
{
    printf("\nplease enter x and y data by order-> ");
    scanf_s("%d%d", &p->x,&p->y);   
}
double distance(point* pA,point*pB)
{
    int x = (pA->x) - (pB->x);
    int y = (pA->y) - (pB->y);
    double d = 0;
    d = sqrt(pow(x, 2) + pow(y, 2));
    return d;
}
polygon* createPolygon()
{
    
    polygon* New=(polygon*)malloc(sizeof(polygon));
    if (New == NULL)
    {
        printf("the alocation failed");
        return NULL;
    }
    else
    {
        printf("the alocation sucsess");
        New->n = 0;
        New->scope = 0;
        New->points = NULL;
        return New;
    }

}



double calculateScope(point* arr, int n)
{
    double d = 0;
    polygon* prev = arr;
    prev->points=(point*)malloc(sizeof(point));
    assert(prev);
    prev = &prev->points[n-1];
    if (n == 0) return d;
    d = distance(prev, arr);    
    return d;

}


int addPoint(polygon* poly)
{
    polygon* ptr = poly;
    ptr->points = (point*)realloc(ptr->points, (ptr->n + 1)*sizeof(point));
    if (ptr == NULL)return 0;
    scanPoint(ptr->points);
    ptr->scope+=calculateScope(ptr->points,ptr->n);
    ptr->n++;
    return 1;
}