Câu 2:
#include <bits/stdc++.h>
using namespace std;
double a,b,c,p,s;
int main()
{
cin>>a>>b>>c;
p=(a+b+c)/2;
s=sqrt(p*(p-a)*(p-b)*(p-c));
cout<<"Chu vi la:"<<fixed<<setprecision(2)<<p*2<<endl;
cout<<"Dien tich la:"<<fixed<<setprecision(2)<<s;
return 0;
}