Program Cong_bac_3;

USES graph,crt; VAR

pi:array[0..3] of real;

u: real;

xi,yi:array[0..3,0..3]of real;

x,y:array[0..3]of real;

m,n,a,c,s:array[0..100]of real;

xdau,Gd,Gm,t,i,j,k,l:integer;

a1,b1:real;

f:text;

(*************************************************)

{-------------Ve he truc toa do------------}

procedure khoitao;

begin

Gd := Detect; InitGraph(Gd, Gm, ' ');

if GraphResult <> grOk then Halt(1);

directvideo:=False;

setbkcolor(1);

setcolor(14);

setviewport(getmaxX div 2,getmaxY div 2,getmaxX,getmaxY,false);

line(-320,0,319,0);

line(319,0,310,-5);

line(319,0,310,5);

line(0,239,0,-240);

line(-5,-230,0,-240);

line(5,-230,0,-240);

outtextxy(-10,-10,'O');

outtextxy(305,10,'x');

outtextxy(10,-230,'y');

end;

(*************************************************)

{thu tuc ve duong cong tron theo thuat toan CASTELJAU}

PROCEDURE ve;

Var

i,j : integer;

BEGIN

moveto(round(x[0]),round(y[0]));

for i:=0 to 3 do

Begin

yi[i,0]:=y[i];

xi[i,0]:=x[i];

End;

u:=0;

while u<=1 do

Begin

for j:=1 to 3 do

Begin

for i:=j to 3 do

Begin

xi[i,j]:=(1-u)*xi[i-1,j-1]+u*xi[i,j-1];

yi[i,j]:=(1-u)*yi[i-1,j-1]+u*yi[i,j-1];

End;

End;

{lineto(round(xi[i,j]),round(yi[i,j]));}

putpixel(round(xi[i,j]),round(yi[i,j]),LIGHTMAGENTA);

delay(0);

u:=u+0.001

End;

END;

(*************************************************)

{-------------Chuong Trinh Chinh------------}

BEGIN

l:=8;

m[0]:=-290;

n[0]:=-200;

m[1]:=-290;

n[1]:=-200;

m[2]:=-190;

n[2]:=-100;

m[3]:=-90;

n[3]:=100;

m[4]:=-60;

n[4]:=60;

m[5]:=-40;

n[5]:=80;

m[6]:=0;

n[6]:=10;

m[7]:=60;

n[7]:=140;

m[8]:=160;

n[8]:=120;

m[9]:=260;

n[9]:=220;

khoitao;

i:=1;

c[0]:=0;

while i<=l do

Begin x[0]:=m[i];y[0]:=n[i];

circle(round(m[i]),round(n[i]),2);

c[i]:=(n[i+1]-n[i])/(m[i+1]-m[i]);

a[i]:=(m[i+1]-m[i])/(m[i+1]-m[i-1]);

s[i]:=(1-a[i])*c[i-1]+a[i]*c[i];

i:=i+1;

x[3]:=m[i];y[3]:=n[i];

circle(round(m[i]),round(n[i]),2);

c[i]:=(n[i+1]-n[i])/(m[i+1]-m[i]);

a[i]:=(m[i+1]-m[i])/(m[i+1]-m[i-1]);

s[i]:=(1-a[i])*c[i-1]+a[i]*c[i];

x[1]:=m[i-1]+(m[i-1]-m[i-2])/3;

y[1]:=n[i-1]+(m[i-1]-m[i-2])*s[i-1]/3;

x[2]:=m[i]-(m[i]-m[i-1])/3;

y[2]:=n[i]-(m[i]-m[i-1])*s[i]/3;

ve;

End;

repeat until

keypressed;

closegraph;

END.