Компьютер должен нарисовать логарифмическую спираль

uses crt,graph;
var
i,j,y,h:longint;
gd,gm:integer;
begin
gd:=detect;
gm:=0;
initgraph(gd,gm,'c:\bp\bgi');
 
line(315,5,315,550);
line(50,250,600,250);
PutPixel(10,10,2);
for i:=1 to 25 do
begin y:=(round(2*exp(0.2*i*ln(2.7)))); {dlia paraboli: y:=(i*i);}
if y>0 then
PutPixel(i+315,250-y,3);
if y<0 then
PutPixel(i+315,250-y,3);
end;
readln;
closegraph;
end.

program LOGSPIR;
uses
  Graph, Crt;
var
  gDriver, gMode: Integer;
  r, a, arad: Real;
begin
  gDriver := Detect;
  gMode := 0;
  InitGraph(gDriver, gMode, '..\bgi');
  ClearDevice;
  SetColor(White);
  Line(0, GetMaxY div 2, GetMaxX, GetMaxY div 2);
  Line(GetMaxX div 2, 0, GetMaxX div 2, GetMaxY);
  while a < 360 * 4 do begin
    arad := a * pi / 180;
    r := 2 * exp(0.2 * arad);
    PutPixel(Round(r*Sin(arad) + GetMaxX / 2),
             Round(r*Cos(arad) + GetMaxY / 2),
             Green);
    a := a + 0.1;
  end;
  while not KeyPressed do Delay(1);
  CloseGraph;
end.