Given a circle o, make two vertical diameters OA, OB,

Let point c oc = 1/40b,

Make point d ∠ OCD = 1/4 ∠ OCA.

Draw point E on the AO extension line so that ∠ DCE = 45 degrees.

Step two:

Make the midpoint of AE m, make a circle with m as the center to pass through point a,

This circle intersects with OB at point F, and then makes a circle with D as the center.

Passing through point f, the circle intersects with straight line OA at G4 and G6.

Step 3:

Through G4, the vertical line of OA and O intersect at P4,

Go through G6 to OA, intersect with vertical line O at P6,

Then the first vertex P4 of a regular heptagon with circle O as the reference circle is the fourth vertex and P6 is the sixth vertex.

With 1/2 arc P4P6 as the radius, all vertices of a regular heptagon can be truncated on this circle.