Draw the bottom projection line (horizontal straight line L) first, take a point X on the straight line as the projection point of AE, the intersection point X as the vertical line H of the straight line L, take the cube side length as the length, intercept the point Y on the straight line H, take the intersection point Y as the straight line M parallel to L, take the root number of the cube side length as the radius, and take the point Y as the center, and intersect with the points U 1 and U2 on the straight line M respectively. So as to obtain a projection.