Нарисовать правильный пятиугольник

uses graphABC;
type point=record
           x,y:integer;
           end;
procedure pent(x,y,r,u:integer);
var p:array[1..6] of point;
    i:byte;
    a,da:integer;
begin
da:=360 div 5;//àíóòðåííèé óãîë ïÿòèóãîëüíèêà
a:=u+90;//íàïðàâëåíèå íà 1 âåðøèíó
for i:=1 to 5 do
 begin
  p[i].x:=x+round(r*cos(a*pi/180)); //îïðåäåëÿåì êîîðäèíàòû âåðøèí ìíîãîóãîëüíèêà
  p[i].y:=y-round(r*sin(a*pi/180)); //îòíîñèòåëüíî öåíòðà îïèñàííîé îêðóæíîñòè
  a:=a+da
 end;
 p[6]:=p[1];//çàìûêàåì ìíîãîóãîëüíèê
 setpencolor(clRed);
 setbrushstyle(bsClear);
 polygon(p,6);//ðèñóåì
end;
var n,xc,yc,x1,y1,r,r1,u:integer;
begin
xc:=windowwidth div 2;
yc:=windowheight div 2;
r:=100;
r1:=60;
u:=0;
 
setpencolor(clBlue);
setbrushcolor(clBlue); //òî÷êà âîêðóã êîòîðîé ïîâîðà÷èâàåòñÿ
circle(xc,yc,2);
x1:=xc+round(r*cos(u*pi/180));//îïðåäåëÿåì òåêóùèå êîîðäèíàòû öåíòðà îêðóæíîñòè
y1:=yc-round(r*sin(u*pi/180));
pent(x1,y1,r1,u);
lockdrawing;//áëîêèðóåì âûâîä íà ýêðàí, ïåðåðèñîâûâàåì â áóôåðå
repeat
clearwindow;
setpencolor(clBlue);
setbrushcolor(clBlue); //òî÷êà âîêðóã êîòîðîé ïîâîðà÷èâàåòñÿ
circle(xc,yc,2);
x1:=xc+round(r*cos(u*pi/180));//îïðåäåëÿåì òåêóùèå êîîðäèíàòû öåíòðà îêðóæíîñòè
y1:=yc-round(r*sin(u*pi/180));
pent(x1,y1,r1,u);
sleep(1000);
u:=u+25; //èçìåíÿåì óãîë(- ïî ÷àñîâîé ñòðåëêå, + ïðîòèâ ÷àñîâîé)
redraw;  //ïåðåðèñîâûâàåì îêíî
until u>=360
end.