#海伦公式: p=C/2; S=sqrt(p*(p-a)(p-b)(p-c)); ">#include<cmath> using namespace std; int main() { double a,b,x; double c,s,p; cin>>a>>b>>x; c=a+b+x; p=c/2.0; s=sqrt(p*(p-a)*(p-b)*(p-x)); printf("circumference=%.2lf area=%.2lf",c,s); return 0; } imp...