Breve experiência com a unit "Graph"

Preview: (a imagem não está correcta relativamente à função seno, mas ilustra bem na mesma o funcionamento do programa)

Código:

program Trigonometria;
uses graph, sysutils, windows;

type TPixel = record
            X, Y : integer;
     end;

var Driver, Modus : smallint;
    Angle : integer;
    i : integer;

const CircleCenter : TPixel = (X:200; Y:200);

function Real2String(const value : real) : string;
begin
     Str(value, Real2String);
end;

function Int2String(const value : integer) : string;
begin
     Str(value, Int2String);
end;

begin
     try
        repeat
              write('Angulo (inteiro) (-360..360)? ');
              readln(Angle);
        until (Angle in [-360..360]);

        DetectGraph(Driver, Modus);
        InitGraph(Driver, Modus, '');

        Circle(CircleCenter.X, CircleCenter.Y, 100);
        Line(CircleCenter.X, 50, CircleCenter.X, 350);
        Line(50, CircleCenter.Y, 350, CircleCenter.Y);

        SetLineStyle(SolidLn,0,ThickWidth);
        SetColor(red);
        Line(CircleCenter.X, CircleCenter.Y,
             round(100*cos((angle*pi)/180)+CircleCenter.X),
             round(CircleCenter.Y-100*sin((angle*pi)/180)));

        SetColor(white);
        OutTextXY(220, 330, 'sin(' + Int2String(angle) + ') = ' + Real2String(sin((angle*pi)/180)));
        OutTextXY(220, 340, 'cos(' + Int2String(angle) + ') = ' + Real2String(cos((angle*pi)/180)));

        SetLineStyle(SolidLn,0,NormWidth);
        Line(400, 200, 800, 200); // Horizontal
        Line(600, 50, 600, 350);  // Vertical
        OutTextXY(610, 50, 'sin(x)');

        for i:=30*round(-2*pi) to 30*round(2*pi) do begin
            PutPixel(600+i, round(200-100*sin((i*pi)/180)), red);
        end;

        SetLineStyle(DashedLn,0,NormWidth);
        SetColor(green);
        Line(CircleCenter.X, round(CircleCenter.Y-100*sin((angle*pi)/180)), CircleCenter.X+400, round(CircleCenter.Y-100*sin((angle*pi)/180)));

        readln; // pausa

        CloseGraph;
     except
           ON e:exception do begin
              MessageBox (0, @(e.message)[1] , 'ERRO!', 0 + MB_ICONHAND);
           end;
     end;
     writeln; write('end'); readln; // pausa
end.