Equiangular lines are lines in space that pass through a single point, and whose pairwise angles are all equal. Picture in 2D the three diagonals of a regular hexagon, and in 3D, the six lines connecting opposite vertices of a regular icosahedron. Mathematicians are not limited to three dimensions, however.
Click here for original story, Mathematicians solve an old geometry problem on equiangular lines
Source: Phys.org