size(400,400);
arc(50, 55, 50, 50, 0, HALF_PI);
noFill();
arc(50, 55, 60, 60, HALF_PI, PI);
arc(50, 55, 70, 70, PI, PI+QUARTER_PI);
arc(50, 55, 80, 80, PI+QUARTER_PI, TWO_PI);

size(400,400);
arc(200, 200, 320, 320, 0, PI+QUARTER_PI, CHORD);

size(400,400);
arc(200, 200, 320, 320, 0, PI+QUARTER_PI, OPEN);

size(400,400);
arc(200, 200, 320, 320, 0, PI+QUARTER_PI, PIE);