Program TINH_DIEN_TICH;
Uses crt;
Procedure HV;
  Var s,a:real;
  Begin
      Writeln('TINH DIEN TICH HINH VUONG:');
      Write('Nhap chieu dai cua canh a = ');readln(a);
      s:=a*a;
     Writeln('Dien tich hinh vuong = ',s:6:2);
  End;
Procedure HT;
Var s,r:real;
Begin
     Writeln('TINH DIEN TICH HINH TRON:');
     Write('Nhap ban kinh R = ');readln(r);
     s:=pi*r*r;
     Writeln('Dien tich hinh tron = ',s:6:2);
End;
Procedure TG;
Var a, b, c,s,p:real;
 Begin
    Writeln('TINH DIEN TICH TAM GIAC:');
    Write('nhap a =');readln(a);
    Write ('nhap b ='); readln (b);
    Write ('nhap c ='); readln (c);
    If ((a + b)> c) and ((b + c)> a) and ((a + c)> b) then
    Begin
         p: = (a + b + c) / 2;
         s: = sqrt (p * (pa) * (pb) * (pc));
         Writeln ('Chu vi tam giac:', 2 * p: 4: 2);
         Writeln ('Dien tich tam giac:', s: 4: 2);
     End
     Else
          Writeln (a, ',', ',', c, 'khong phai la ba canh cua tam giac');
Kết thúc;
Thủ tục CN;
Var a, b, s: real;
Begin
     Writeln ('TINH DIEN TICH HINH CHU NHAT:');
     Write ('Nhap chieu dai a ='); readln (a);
     Write ('Nhap chieu rong b ='); readln (b);
     s: = a * b;