Draw a circle on the coordinate axis with the origin as the center, choose a diameter AB to divide the diameter n equally, then draw a circle with A or B as the origin and the diameter of the origin as the radius, and the X axis intersects C D at two points. When the diameter n is equal, there are N+ 1 points, which are recorded as 0123 ... n n (who is the radius of the second circle drawing, counting from the other). If n is an odd number, it is useless to take all singularities (even if it is not selected). For example, N points connecting C 1D3, C5, D7 and C9DN ... in order to divide the circle into n equal parts.