Radius gauge and reverse engineering

[prm]

Paul,

I always like to find an easier way regards of where it comes from but I just don't follow your formula. Please show the full derivation. I assume that brackets could enclose the 2*h as (2*h) for clarity and that it is not ((s^2 + h^2) / 2)*h, to remove any ambiguity. In any case I am just not getting it, sometimes we get tunnel vision.

Tony,

I have produced a document with the derivation. It is very convenient that the r^2 terms cancels out and leaves a remarkably simple formula.

Cheers,
Paul