4 equal division: to find any diameter, draw an arc at both ends with a compass with a length greater than the radius, and the intersection of the two arcs is connected to find two intersections with the circumference. In this way, the two intersections, plus the two endpoints of the diameter, form four equal points.
5 equal parts is to draw a five-pointed star and find 5 endpoints: refer to others';
Method 1: first draw a circle on the paper with a compass, and then draw two mutually perpendicular diameters AC and BD of the circle; Then take C and D as the center, the radius of diameter BD as an arc, and the two arcs intersect at point E, and OE is approximately equal to the side length of the inscribed circle of a regular Pentagon. Starting from point A and taking OE as the radius, cut out four points on the circumference in turn to connect two adjacent points. The obtained regular pentagon is called the inscribed regular pentagon of a circle (because its five vertices are all on the circle). With these five vertices. It is easy to draw a five-pointed star.