# Circular Slide Rule

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To multiply two numbers and , slide the inside scale so that the 1 on it is over on the outside scale. Find on the inside scale; then is across from on the outside scale.

Contributed by: Izidor Hafner (August 2012)

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

This slide rule uses the identity .

Reference

[1] J. Bryant and C. Sangwin: *How Round Is Your Circle?: Where Engineering and Mathematics Meet*, Princeton, NJ: Princeton University Press, 2008, pp. 240–241.

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