Python

a = int(input("Nhap a = "))
print("Dien tich can tinh = {:.2f}".format(a**2-(((a/2)**2)*3.14))

CPP

#include <iostream>
#include <cmath>
using namespace std;
int main() {
    int a;
    cout << "Nhap a = ";
    cin >> a;
    cout << endl;
    cout << "Dien tich can tinh = " << a*a-(((a/2)*(a/2))*3.14);
    return 0;
}

Pascal

uses crt;
var a: integer;
begin
clrscr;
write('Nhap a = ');
readln(a);
writeln ('Dien tich can tinh = ', a*a-(((a/2)*(a/2))*3.14):2:2)
end.

uses crt;
var a,v,t:real;
begin
clrscr;
write('Nhap  a = '); readln(a);
v:=a*a;
t:=(a/2)*(a/2)*3.14;
write('Dien tich can tim = ',v-t:0:2);
end.