1

We manufacture circular things that have parallel lines across them, evenly spaced. Someone drew a picture here https://i.stack.imgur.com/3LPtM.png though we don't have a chord through the center.

How to sum the lengths of all the parallel chords given radius and the fixed perpendicular distance between chords?

Presently, I use the chord formula based upon perpendicular distance from center: $2({\sqrt(r^2-h^2)}$, h is perpendicular distance from center

In Excel, I have cell for r and cells for h and enough cells containing the chord formula, and finally the sum.

How to get the sum of all these chords given r, h?

Additional point: We do not ever have a chord passing through the center. In other words, there are always and even number of chords. This defines the position of the first chord.

Example:

r = 30 (it's meters, by the way, these things are huge)

h = 1

So the first chord from center is $h/2 = 0.5$ perpendicularly from center. Its length is: $2({\sqrt(30^2-0.5^2)} = 29.17$

The next chord is h further away from center, ie $0.5 + h = 1.5$ Its length: $2({\sqrt(30^2-1.5^2)} = 28.95$

Follow up question: what is the Excel formula (if it even possible with normal Excel formulas)?

Thanks so much for reading even if you do not reply!

Wish I could add tags: sum parallel chords, but not allowed.

Questions here that sound similar but do not fit:

Sum and average length of chords

Circle Chord Length Given other Chord

Sum and average length of constrained chords

  • If it is helpful there are calculators such as: https://www.desmos.com/calculator/lejeoyuo81 which can compute summations directly. – mrtechtroid Jan 17 '23 at 09:07
  • Thanks! That looks useful in some situations though in this case I need it offline for numerous permutations. – Aleksander K Jan 17 '23 at 10:43
  • Can anyone suggest another forum where this would be appropriate? Have I expressed the question clearly? – Aleksander K Jan 20 '23 at 07:54

0 Answers0