Spiral

A spiral is a curve which turns around some central point, getting progressively closer to or farther from it (depending on which way you follow the curve). In polar coordinates, then, r is an monotonic function of θ.

Some of the more important sorts of spirals include:

• The Archimedean spiral - r = a + bθ
• The Hyperbolic spiral - r = a/θ
• The Logarithmic spiral - r = ab^θ; approximations of this found in nature
• Fermat's spiral - r = θ^1/2
• The Lituus - r = 1/θ^1/2