#include <stdio.h> #include<math.h> int main() { double a, b, c; while (scanf("%lf %lf %lf", &a, &b, &c) != EOF) { // 关键是使用余弦定理 double n1, n2, n3; n1 = pow(a, 2) + pow(b, 2) - pow(c, 2); n2 = pow(a, 2) + pow(c, 2) - pow(b, 2); n3 =...