In article <email@example.com>, <firstname.lastname@example.org> wrote: >Paul Hughett (email@example.com) wrote: > >One of my slide rules, for which I haven't had the manual for years, has >an odd index mark on it. It's labelled with an uppercase 'C' and is >located at 1.125 (or there about). > >I played around trying to figure out what it was for but nothing made any >sense.
C = sqrt(4/pi) = 1.128379... (not calculated with a slide rule!);
If A is the area of a circle of diameter d, then d = C*sqrt(A) and A = (d/C)^2.
John Harper, School of Mathematical and Computing Sciences, Victoria University, Wellington, New Zealand e-mail firstname.lastname@example.org phone (+64)(4)463 5341 fax (+64)(4)463 5045