Câu 1:

#include<iostream>
using namespace std;
int main()
{
    
    int n,t,na;
    cout<<"Ngay: "; cin>>n;
    cout<<"Thang: "; cin>>t;
    cout<<"Nam: :"; cin>>na;
    cout<<n<<"/"<<t<<"/"<<na;
}

Bài 2:

#include<iostream>
using namespace std;
int main()
{
    double s;
    cout<<"S= "; cin>>s;
    cout<<"Chu vi: "<<2*s*3.14<<endl;
    cout<<"Dien tich: "<<s*s*3.14;
    return 0;
}

Câu 1:

#include <bits/stdc++.h>
using namespace std;
int main() {
   int n,t,na;
   cout<<"Nhap ngay, thang, nam: "; cin>>n>>t>>na;
   cout<<n<<"/"<<t<<"/"<<na<<endl;
}

Câu 2:

#include <bits/stdc++.h>
using namespace std;
int main() {
   float r;
   cout<<"Nhap ban kinh duong tron: "; cin>>r;
   cout<<"Chu vi: "<<setprecision(1)<<fixed<<r*2*3.14<<endl;
   cout<<"Dien tich: "<<setprecision(1)<<fixed<<r*r*3.14<<endl;
}