#include <iostream>
#include <math.h>
int main() {
setlocale(LC_ALL, "Russian");
double a = 0;
double b = 0;
double c = 0;
double p = 0;
std::cout << "Введите три стороны треугольника\n";
std::cin >> a >> b >> c;
if ((a == b) && (b == c)) {
std::cout << "треугольник равносторонний\n";
}
if ((a == b) || (a == c) || (b == c)) {
std::cout << "треугольник равнобедренный\n";
}
if ((a + b == c) && (a + c == b) && (b + c == a)) {
std::cout << "треугольника не существует\n";
} else {
p = a + b + c;
}
double s = sqrt(p * (p - a) * (p - b) * (p - c));
std::cout << "S = " << s << '\n';
}
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