V8/usr/lib/ideal/lib/ARC

.IS
ARC {
	var a1, b1, c1,
	a2, b2, c2;
	start ~ center + abs(radius)*cis(startang);
	end ~ center + abs(radius)*cis(endang);
	midway ~ center + abs(radius)*cis(midang);
	im(start-center)*re(cis(startang))
	~ re(start-center)*im(cis(startang));
	im(end-center)*re(cis(endang))
	~ re(end-center)*im(cis(endang));
	im(midway-center)*re(cis(midang))
	~ re(midway-center)*im(cis(midang));
	a1 ~ 2*(re(end)-re(start));
	b1 ~ 2*(im(end)-im(start));
	c1 ~ -re(start)*re(start) - im(start)*im(start)
	+ re(end)*re(end) + im(end)*im(end);
	a2 ~ 2*(re(end)-re(midway));
	b2 ~ 2*(im(end)-im(midway));
	c2 ~ -re(midway)*re(midway) - im(midway)*im(midway)
	+ re(end)*re(end) + im(end)*im(end);
	a1*re(center) + b1*im(center) ~ c1;
	a2*re(center) + b2*im(center) ~ c2;
	startang ~ atan2 (start - center);
	midang ~ atan2 (midway - center);
	endang ~ atan2 (end - center);
	radius ~ abs (start - center);
	radius ~ abs (midway - center);
	radius ~ abs (end - center);
	midway ~ start;
}
.IE