The difference between these lengths is a - (length of AB) =Ī - = a(3√2 - 4) / 2 = a(3/√2 - 2). The length, a, from each corner of the square must be shortened so its length is equal to the length of AB in the diagram in Step 7 when n = 3. If the distance between each of the two marks on each outer side of the square grid in the 2013 Instructables is of length a, then these marks must be shifted (see diagram in Step 6) so as to reduce the lengths of the distances between the outer corners of the square grid and the marks nearest them on the outer sides of the square grid. We derive an expression for the amount by which the marks on each outer side of the square grid, as described in the 2013 Instructables article, need to be moved to create a regular octagon from the non-regular octagon. In this final step we return to the method described in the 2013 Instructables. To make a regular octagon from the octagon described in the 2013 Instructables article, both pairs of marks on each of the outer sides of the square grid in the 2013 Instructables article need to be shifted by about 12% towards the outer corners of the square grid before drawing lines between the nearest pairs of the newly created marks nearest to adjacent outer corners on the outer sides of the square grid. While the method described in the 2013 Instructables article results in an octagon, this octagon is not a regular octagon. The above diagram shows that the corners of a regular octagon do not coincide with the intersection of the blue lines with the outer sides of the grid. drawing lines between the pairs of marks nearest to the adjacent outer corners of the square grid.placing marks on the sides of the square to indicate the points of division.dividing the sides of the square into thirds.The author of this Instructables describes a simple way to draw an octagon in a square which involves: One feature of the grid in the above diagram relates to an Instructables published in 2013. This diagram shows a regular octagon (red) inside a blue 3 by 3 square grid. Using the 6 by 6 square grid in Step 5 and colouring the even lines in this grid blue, results in the diagram shown in this step.
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