Drawing a Logarithmic Spiral

This Demonstration shows an approximation of the logarithmic spiral . Draw equally spaced rays from the origin . The point is on the polar axis at a distance 1 from the origin. The point is on the ray at the distance . So and are on the spiral. Draw a point so that the triangles and are similar. From , we get . On the ray , draw a point at distance ; this point will be on the spiral. Continue in this way. Note that 1, , , … form a geometric sequence.


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[1] A. A. Savelov, Plane Curves (in Croatian), Zagreb: Školska knjiga, 1979, pp. 264–265.
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