program Begin_15
uses crt-
var x1,x2,x3,y1,y2,y3,a,b,c,s,p : real-
begin
clrscr-
write(‘x1=’)-readln(x1)-
write(‘y1=’)-readln(y1)-
write(‘x2=’)-readln(x2)-
write(‘y2=’)-readln(y2)-
write(‘x3=’)-readln(x3)-
write(‘y3=’)-readln(y3)-
a:=sqrt(sqr(x1-x2)+sqr(y1-y2))-
b:=sqrt(sqr(x2-x3)+sqr(y2-y3))-
c:=sqrt(sqr(x3-x1)+sqr(y1-y3))-
p:=(a+b+c)/2-
s:=sqrt(p*(p-a)*(p-b)*(p-c))-
write(‘s=’,s)-
readln-
end.