#include <stdio.h> int main() { double a, b, c; scanf("%lf %lf %lf", &a, &b, &c); double p = (a + b + c) / 2; //海伦公式求三角买面积S=√[p(p-a)(p-b)(p-c)] printf("circumference=%.2lf area=%.2lf", (a + b + c), sqrt(p * (p - a) * (p - b) * (p - c))); ...