A planar transcendental curve the equation of which in polar coordinates has the form
To each value of $\phi$ correspond two values of $\rho$ — a positive and a negative one. The Fermat spiral is centrally symmetric relative to the pole, which is a point of inflection. It belongs to the class of so-called algebraic spirals.
They were first studied by P. Fermat (1636).
-  A.A. Savelov, "Planar curves" , Moscow (1960) (In Russian)
|[a1]||J.D. Lawrence, "A catalog of special plane curves" , Dover, reprint (1972)|
Fermat spiral. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Fermat_spiral&oldid=52724