in reply to N circles around a circle.

sub r_outer { ($R_center * sin( $pi / $n)) / (1 - sin $pi / $n) }

semi-tested :)

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Re^2: N circles around a circle.
by pryrt (Abbot) on Feb 20, 2017 at 14:04 UTC

    For the curious, the derivation for this is the same as for this geometry@SE post, except that here, the angle θ is known (θ = 2π/N) and you are trying to solve for r, rather than the other way around.

Re^2: N circles around a circle.
by BrowserUk (Patriarch) on Feb 20, 2017 at 05:56 UTC

    Perfect. Thank you.