PPT Slide
A form is a characteristic shape of a class of objects which share typical features.
A good example of this are seashells.The following web site shows a Nautilus seashell. Notice the spiral shape of the shell. In fact, the rim of the shell traces out a logarithmic spiral, which can be described in polar coordinates by the equation
This basic mathematical form was originally proposed by the
French mathematician René Descartes, in 1638. The following is a link to a picture which shows how perfectly this mathematical form matches that of the Nautilus.
Other seashells also have a form described by a logarithmic spiral extended into three dimensions.