квадрат 1

#include <iostream>
#include <cmath>
#include <algorithm>
#include <iomanip>

using namespace std;

struct direct
{
 double k = 0, b = 0;
 double parametr = 0;
};

struct vershina
{
  double x, y;
};

direct storona (vershina first, vershina second)
{
  direct stright;
  if(first.x - second.x != 0)
  {
    stright.k = (first.y - second.y)/(first.x - second.x);
    stright.b = first.y - stright.k*first.x;
  }
  else stright.parametr = first.x;

  return stright;
}

vershina result (direct one, vershina head, double dlina)
{
  vershina result;
  direct two;
  if (one.k != 0)
    two.k = -1/one.k;
  two.b = head.y - head.x*two.k;
  vershina times;

  times.x = head.x-1;
  times.y = two.k*times.x+two.b;

  times.x = head.x - times.x;
  times.y = head.y - times.y;

  double koeff = sqrt((dlina*dlina)/(times.x*times.x + times.y*times.y));

  result.x = times.x*koeff;
  result.x = head.x - result.x;

  result.y = times.y*koeff;
  result.y = head.y - result.y;

  return result;
}

int main ()
{
  vershina A, B, C, D;
  cin >> A.x >> A.y >> B.x >> B.y;
  direct AB, DB;

  double dlina = sqrt((A.x - B.x)*(A.x - B.x) + (A.y - B.y)*(A.y - B.y));

  AB = storona (A, B);
  D = result(AB, A, dlina);
  DB = storona (D, B);
  C = result(DB, A, dlina*sqrt(2));

  cout << C.x << " " << C.y << " ";
  cout << D.x << " " << D.y << " ";
}