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Mirbek

Формулы

Jan 28th, 2022
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  1. /***
  2. Геомтерия
  3. ***/
  4. #include <bits/stdc++.h>
  5.  
  6. using namespace std;
  7.  
  8. double dist(double x, double y, double x2, double y2) {
  9.     double d = sqrt((x - x2) * (x - x2) + (y - y2) * (y - y2));
  10.     return d;
  11. }
  12.  
  13. double area(double x, double y, double x2, double y2, double x3, double y3) {
  14.     double a = dist(x, y, x2, y2);
  15.     double b = dist(x, y, x3, y3);
  16.     double c = dist(x2, y2, x3, y3);
  17.     double u = (a + b + c) / 2;
  18.     double S = sqrt(u * (u - a) * (u - b) * (u - c));
  19.     return S;
  20. }
  21.  
  22. int main(){
  23.     int n;
  24.     cin >> n;
  25.  
  26.     int x[n + 1], y[n + 1];
  27.     for (int i = 1; i <= n; i++) {
  28.         cin >> x[i] >> y[i];
  29.     }
  30.  
  31.     double s1 = 0, s2 = 0;
  32.     for (int i = 1; i < n; i++) {
  33.         s1 += x[i] * y[i + 1];
  34.         s2 += y[i] * x[i + 1];
  35.     }
  36.  
  37.     s1 += x[n] * y[1];
  38.     s2 += y[n] * x[1];
  39.  
  40.     double S = fabs(s1 - s2) / 2;
  41. }
  42.  
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