Quandaries and Queries


I understand there is a simple calculation to determine the sides of an octagon when you know the distance across the parallel flats. something like .447 . can you help? Private home owner with octagon skylights see www.domehome.ca for details. thanks


Hi Royce,

I copied one of the images of your skylight from your website.

In the diagram below L is the distance between the sides and s is the length of a side.

From the diagram

L = s + 2 a

Triangle ABC is a right triangle, and hence from Pythagoras Theorem

a2 + a2 = s2


a = s /√2


L = s + 2 a = s + 2  s /√2 = s (1 + √2) = 2.4142 s


s = 0.4142 L