норма

#include <iostream>
#include <cmath>

	using namespace std;

	double otrezok(double x1, double y1, double x2, double y2)
	{
		double result;
		result = sqrt(pow(x1 - x2, 2) + pow(y1 - y2, 2));
		return result;
	}

	bool IsTriangle(double a, double b, double c)
	{
		double eps = 1e-3; // точность вычислений до одной тысячной
		return (b + c - a > eps) && (a + c - b > eps) && (a + b - c > eps);
	}

	int main()
	{
		const int n = 4;
		double x[n], y[n], a, b, c;
		int count = 0;
		cout << "Input coords of points:" << endl;
		for (int i = 0; i < n; ++i)
		{
			cout << "Point " << i + 1 << endl;
			cout << "\tx" << i + 1 << ": ";
			cin >> x[i];
			cout << "\ty" << i + 1 << ": ";
			cin >> y[i];
		}
		for (int i = 0; i < n - 2; ++i)
			for (int j = i + 1; j < n - 1; ++j)
				for (int k = j + 1; k < n; ++k)
				{
					a = otrezok(x[i], y[i], x[j], y[j]);
					b = otrezok(x[j], y[j], x[k], y[k]);
					c = otrezok(x[i], y[i], x[k], y[k]);
					if (IsTriangle(a, b, c))
						++count;
				}
		cout << "Number of triangles: " << count << endl;
		system("pause");
	}