48

Part of 1977 IMO Longlists

Problems(1)

Prove that 2a ≤ P ≤ 3a - [ILL 1977]

Source:

The intersection of a plane with a regular tetrahedron with edge

a

is a quadrilateral with perimeter

P.

2a \leq P \leq 3a.

geometry3D geometrytetrahedronperimetergeometry unsolved