Isosceles set $i(2)$

The vertices and center of a regular pentagon, an isosceles set of 6 points in the plane, with segments colored by length

The size of the largest set of points in $\mathbb{R}^{2}$ in which every three points form an isosceles triangle.

Value: $6$ Verified lower bound

Verified bounds

Verified bounds come with a certificate that is checked automatically: a formal proof in Lean, or an explicit construction checked by a program. Submit a certificate.

Updates from the literature