How to make a regular octagon out of square paper

(page 10)

17th picture of regular octagon out of square paper

17.

Apply three valley-fold of the step #16 and then unfold.

Prepare to re-apply the valley-fold of the step #14.

18th picture of regular octagon out of square paper

18.

Apply the valley-fold of the step #17.

Prepare to cut the paper off along two dotted lines.

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