x=radians
y=radius

1. cos(x)*y

Of course i can use a calc, but i have not idea how calc calculate it. How?

1. size(500, 500);
   background(255);
   smooth();
   fill(255,255);
   stroke(0);
   fill(255);
   ellipse(250,250,475,475);
   for (int y=0;y<height;y+=3) {
   line(y,height-height,y,height);
   }