A curve which can be turned continuously inside an Equilateral Triangle. There are an infinite number of delta curves, but the simplest are the Circle and lens-shaped -biangle. All the curves of height have the same Perimeter . Also, at each position of a curve turning in an Equilateral Triangle, the perpendiculars to the sides at the points of contact are Concurrent at the instantaneous center of rotation.

**References**

Honsberger, R. *Mathematical Gems I.* Washington, DC: Math. Assoc. Amer., pp. 56-59, 1973.

© 1996-9

1999-05-24