Regular Pentagon: straight line AB, cross-section AB, BC⊥BA, AB = 2bc (the middle vertical line of AB), connected to AC. Make a circle with C as the center, BC as the radius, AC and P intersect, then A as the center, AP as the radius, AB and M as the center, MB as the radius, AB's perpendicular line at D, A and D as the center, AD and AB as the radius, at E point, B and D as the center, BD and AB as the radius, and at F point, connect AD and BD. A pentagon is a regular pentagon.
Regular hexagon: make ⊙O, make a straight line AB through point O, intersect ⊙O in A and B, take A and B as the center, and AO and BO as the radius, and make circles intersect ⊙ O at C, D, E and F respectively (C and E are on the same side of AB), connecting AC, AD, BE, BF and CD.
Regular octagon: make a regular quadrilateral ABCD, connect AC and BD at O, take O as the center and OA as the radius, then A, B, C and D are on the circle, and the perpendicular lines of AB and BC are at E, F, G and H ⊙O(E and H are on the same side of AC), and connect AE, AG, BE and D.
Regular dodecagon: make a regular hexagon on a circle, so that the perpendicular lines of each side intersect at six points, and connect these twelve points in turn, then this regular dodecagon is a regular dodecagon. (Regular decagon and regular hexagon can do the same).