What the landlord said is not detailed! I have come to three conclusions: 1. The center of 18 is on the great circle and the radius of the great circle is 7 19.85. 2: 18 circle is inscribed with a great circle with a radius of 844.69. 3: 18 circle circumscribes a great circle with a radius of 595.04. Drawing method: Draw two vertical lines on a straight line, divide them into 18 equally (first draw a ray from a horizontal straight line with rays, and then array it), draw one of the small circles of 18 with a circle (tangent, tangent and radius), and then array it into a circle! Then draw a big circle with a circle (two points) and mark or measure it! If you don't understand, you can ask.