Tartaglia's
stellated truncated hexahedron from his 1543 edition of Euclid's
"Elements."



Evolute of a Plane Curve  The
Family of Normals
Did you know . . .
Please note the second degree term is missing. Moreover, neither
Tartaglia nor Cardan knew of negative and/or imaginary solutons to
equations. However, Cardan was the first to notice a cubic might
have three roots and wrote the negative solutions were "fictitious."

A brief list of
references that should
be in most university libraries.

From the
authors of Deposit # 80 . . .
Bains, Manjinder S. and J. B. Thoo
, The Normals to a Parabola and the Real Roots of a Cubic, The College Mathematics Journal, 38
(4) September 2007, pp. 272277. 
Gray,
Alfred, Modern Differential Geometry of
Curves and Surfaces with MATHEMATICA^{®}, CRC Press,
1998, p. 1027.

Lockwood,
E. H., A Book of Plane Curves,
Cambridge University Press, 1961, pp. 167171. 
Weisstein,
E. W., CRC Concise Encyclopedia of Mathematics, CRC Press,
1999, pp. 589  590. See Evolute.

