1) uses crt;
var a  : integer;
function cvi(x : integer) : integer;
begin clrscr;
cvi:=4*x;
end;
begin clrscr;
write('Nhap do dai canh :'); readln(a);
write('Chu vi :', cvi(a));
readln
end.

2) uses crt;
var a  : integer;
function dt(x : integer) : integer;
begin clrscr;
dt:=x*x;
end;
begin clrscr;
write('Nhap do dai canh :'); readln(a);
write('Dien tich hinh vuong :', dt(a));
readln
end.

3) uses crt;
var r  : real;
function dt(x : real) : real;
begin clrscr;
dt:=x*2*3.14;
end;
begin clrscr;
write('Nhap ban kinh hinh tron :'); readln(r);
write('Chu vi hinh tron :', dt(r):2);
readln
end.

1.

#include<bits/stdc++.h>
using namespace std;
int cv(int a)
{
    return a*4;
}
int main()
{
    int n;
    cout<<"Nhap canh hinh vuong: ";
    cin>>n;
    cout<<"Chu vi hinh vuong: "<<cv(n);
    //samon247
    return 0;
}

2.

#include<bits/stdc++.h>
using namespace std;
int dt(int a)
{
    return a*a;
}
int main()
{
    int n;
    cout<<"Nhap canh hinh vuong: ";
    cin>>n;
    cout<<"Dien tich hinh vuong: "<<dt(n);
    //samon247
    return 0;
}

3.

#include<bits/stdc++.h>
using namespace std;
#define pi M_PI
float cv(int r)
{
    return r*2*pi;
}
int main()
{
    float r;
    cout<<"Nhap ban kinh: ";
    cin>>r;
    cout<<"Chu vi hinh tron: "<<cv(r);
    //samon247
    return 0;
}

4.

#include<bits/stdc++.h>
using namespace std;
#define pi M_PI
float cv(int r)
{
    return r*2*pi;
}
int main()
{
    int a;
    float r;
    cout<<"Nhap canh tam giac: ";
    cin>>a;
    r=a/sqrt(3);
    cout<<"Chu vi hinh tron: "<<cv(r);
    //samon247
    return 0;
}