MathDB
intersection of any plane with surface with >1 points is a circle, sphere

Source: 1965-66 Germany R4 12.6 https://artofproblemsolving.com/community/c3208025_

October 12, 2024
spheregeometry3D geometry

Problem Statement

Prove the following theorem: If the intersection of any plane that has more than one point in common with the surface FF is a circle, then FF is a sphere (surface).