lituus.nb.zip.The Lituus curve is studied by Roger Cotes↗ in 1722 [Robert C Yates 1952].
The word lituus↗ means a curved staff used by the augurs in quartering the heavens. (see crosier↗), or A kind of trumpet of a somewhat curved form and shrill note.
above: A crosier of Archbishop Heinrich of Finstingen, 1260-1286. (full size) (Source↗ 2008-03)
Lituus is a spiral described by the polar equation r == 1/Sqrt[θ].
The curve is asymptotic to the positive x-axis, and the other end spiral in towards the pole. The above image is a plot from 0.1 to 20*π. As θ approachs infinity, the curve approaches the origin.
Polar equation: r == 1/Sqrt[θ].
It has the property that a circular sector produces the same area. That is, suppose P is a point on the curve, and X a point on the asymptote OP distance from the origin O. Suppose the area of the circular sector OPX is A. As P moves towards the center on the curve, the area remains the same.
Lituus_spiralThe inverse of Lituus with respect to the center is the parabolic spiral.
The lituus spiral is a recurring shape in art called Volute↗.
above: The Scroll↗ of a unfinished violin.
Archimedes' spiral, equiangular spiral, Mathematics of Seashell Shapes.
See: Websites on Plane Curves, Printed References On Plane Curves.
Robert Yates: Curves and Their Properties.
Wikipedia: Lituus↗.
The MacTutor History of Mathematics archive↗.
Carving the scroll in making the violin: http://www.violins.demon.co.uk/making/carvescroll.htm.
© 2002-2008 by Xah Lee.
