bài 1:
program dien_tich_hinh_vuong;
uses crt;
var a:integer;
      s:longint;
begin
clrscr;
writeln('nhap vao 1 canh cua hinh vuong: ');readln(a);
s:=a*a;
writeln('dien tich hinh vuong la: ',s);
readln
end.
bài 2:
program dien_tich_tam_giac_2;
uses crt;
var a,h:integer;
      s:real;
begin
clrscr;
writeln('nhap vao duong cao: ');readln(h);
writeln('nhap vao canh tuong ung voi duong cao trong tam giac: ');readln(a);
s:=(a*h)/2;
writeln('dien tich tam giac: ',s:4:2);
readln
end.
bài 3:
program hinh_binh_hanh;
uses crt;
var a,n:integer;
      s:longint;
begin
clrscr;
writeln('nhap vao canh a: ');readln(a);
writeln('nhap vao duong cao: ');readln(h);
s:=a*h;
writeln('dien tich hinh binh hanh la: ',s);
readln
end.