Given The Side Of An Octagon, To Find The Width. (Fig. 63.)

Given the side ab of the octagon, locate point c by resting equal figures of Bl. and To. upon a and b.

Apply Formula 1.

W = width of octagon.

Formula 1. W = ab + 2ac.

Another method is to reduce the side of the octagon to an inch scale, and to make two parallel lines upon the bevel board as far apart as the length of the given side. Lay the square with the figures 7 and 17 exactly coinciding with the lines. The end of the square d and the angle e will give two points which denote the width of the completed octagon. This is simply reversing the method described under Topic 40, B; and if the work is done accurately, quite satisfactory results may be obtained.

FlG. 62. - To Octagon a Given Timber.

Method 4.

Fig. 63. - Given the Side of an Octagon to find the Width.