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.