Lateral surface area

The area of the lateral surface of the truncated cone is closely related to the area of the lateral surface of the truncated pyramid, since for proof we enter a truncated pyramid in the cone, which tends to coincide with the cone as much as possible, that is, the number of its faces tends to infinity, and their size (area) tends to zero. Accordingly, the perimeters of the bases of the truncated pyramid will tend to reach the circumference of the bases of the cone, and the height - apothems.