program BT;
uses crt;
var a,b,c,p,S: real;
Begin
clrscr;
write('Nhap canh a: '); readln(a);
write('Nhap canh b: '); readln(b);
write('Nhap canh c: '); readln(c);
if (a>0) and (b>0) and (c>0) then
if (a+b > c) and (b+c > a) and (a+c > b) then
begin
p:=(a+b+c)/2;
S:=p*(p−a)*(p−b)*(p−c);
write('Dien tich tam giac = ',sqrt(S):2:2);
end
else write(a:2:2,', ',b:2:2,', ',c:2:2,' khong la 3 canh tam giac');
readln
End.