Steps of this construction:
- Use the green circles and blue lines to construct the yellow pentagon, along with its green inscribed pentagram.
- Construct the equilateral triangle shown in gray. This is needed to obtain a twelve degree angle. The triangle is needed for its sixty degree angle, because 72 – 60 = 12. (The 72 degree angle is found inside the pentagon.)
- Identify the twelve degree angle shown in bold. A twelve degree angle is needed because 360 / 30 = 12.
- Use the red circles to complete the thirty sides of the regular triacontagon, which is shown with bold black segments, inscribed inside a large, bold, red circle.