answer.code: In function ‘double cos(Point, Point, Point)’:
answer.code:30:55: error: ‘sqrt’ was not declared in this scope
   30 |     return (dis(a, b) + dis(b, c) - dis(a, c)) / (2 * sqrt(dis(a, b)) * sqrt(dis(b, c)));
      |                                                       ^~~~
answer.code: In function ‘int main()’:
answer.code:48:5: error: ‘sort’ was not declared in this scope; did you mean ‘short’?
   48 |     sort(list, list + n, cmp);
      |     ^~~~
      |     short