- Draw circle O. Find points A and B on circle O, so that OA _|_ OB.
- Find M, the midpoint of OB. Draw a circle at M, crossing A. Circle M crosses
OB at C and crosses OA at D.
- Draw a circle at A, crossing C. Circle A crosses circle O at points E and F.
- Points E, A, F, and D are points of the decagon. Use them to find the rest!