# Fermat spiral

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A planar transcendental curve the equation of which in polar coordinates has the form

To each value of correspond two values of — 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).

Figure: f038420a

#### References

 [1] A.A. Savelov, "Planar curves" , Moscow (1960) (In Russian)