var l1,l2,lp,x1,y1,x2,y2,l,x3,y3,a1,a2,b1,b2,c1,c2,xp,yp:real;
begin
readln(x2,y2,x3,y3,x1,y1,l);
l1:=sqrt(sqr(x1-x2)+sqr(y1-y2));
l2:=sqrt(sqr(x1-x3)+sqr(y1-y3));
if (l1<l) and (l2<l) then begin
writeln('0.00'); writeln('0.00'); end else
begin
   a1:=y3-y2;
   b1:=x2-x3;
   c1:=y2*x3-x2*y3;
   a2:=-b1;
   b2:=a1;
   c2:=-(a2*x1+b2*y1);
   if (b1<>0) and (b2<>0) then
   begin
      xp:=(b2*c1-b1*c2)/(b1*a2-b2*a1);
      yp:=(-c1-a1*xp)/b1;
   end;
   if (b2=0) then
   begin
      yp:=-c1/b1;
      xp:=-c2/a2;
   end;
   if (b1=0) then
   begin
      xp:=-c1/a1;
      yp:=-c2/b2;
   end;
   if (((xp>=x2) and (xp<=x3)) or ((xp<=x2) and (xp>=x3))) and
      (((yp>=y2) and (yp<=y3)) or ((yp<=y2) and (yp>=y3)))then
      lp:=sqrt(sqr(x1-xp)+sqr(y1-yp))
      else if l1<=l2 then lp:=l1 else lp:=l2;
   if lp>=l then writeln(lp-l:0:2)
        else writeln('0.00');
   if l1<=l2 then
      if l2>=l then writeln(l2-l:0:2,' ')
        else writeln('0.00');
   if l2<l1 then
      if l1>=l then writeln(l1-l:0:2,' ')
        else writeln('0.00');
end;
end.

Please, help me...

Maybe real numbers comparison doesn't work well.
Try to change
a = b  for  abs(a - b) < EPS
a < b  for  a < b - EPS
a <= b  for  a - EPS < b,
where EPS is a rather little positive number like 1e-10,
for all real numders a and b in your program.

Also make sure you never divide by zero.