The center distance refers to the radius of the inscribed circle of a regular polygon. The side length of a regular hexagon is equal to the radius of its circumscribed circle, and its vertex is equal to 3/2 times of the side length. The vertex of a triangle is the radius of its inscribed circle. The vertex of a regular polygon is the radius of its inscribed circle. A regular polygon has a circumscribed circle, and the central angle of each side is actually the central angle of the arc opposite to this side.