::sin() and ::cos()

I've seen a code including math.h, and then running:

        item->setPos(::sin((i * 6.28) / 10.0) * 150,
                     ::cos((i * 6.28) / 10.0) * 150);

What's the concret meaning of those "::"? Are them for referring to the global namespace (so sin() could be used)?

Thanks!