Illustration of a conical bifrustum created by three parallel planes of circles with the middle plane…

Illustration of a decagonal bifrustum created by three parallel planes of decagons with the middle plane…

Illustration of a hexagonal bifrustum created by three parallel planes of hexagons with the middle plane…

Illustration of a octagonal bifrustum created by three parallel planes of octagons with the middle plane…

Illustration of a square bifrustum created by three parallel planes of squares with the middle plane…

Illustration of two parallel planes. "Two planes perpendicular to the same straight line are parallel."

Two parallel planes perpendicular to a line (AB). "A straight line perpendicular to one of two parallel…