A figure used in many Asian cultures to symbolize the unity of the two "opposite" female and male elements, the "yin" and "yang." The solid and
hollow parts composing the symbol are similar and combine to make a circle.
Each part consists of two equal oppositely oriented semicircles
of radius 1/2 joined at their edges, plus a semicircle
of radius 1 joining the other edges.
Dixon, R. Mathographics. New York: Dover, p. 11, 1991.Gardner, M. "Mathematical Games:
A New Collection of 'Brain-Teasers.' " Sci. Amer.203, 172-180,
Oct. 1960.Gardner, M. "Mathematical Games: More About the Shapes
that Can Be Made with Complex Dominoes." Sci. Amer.203, 186-198,