Integer triangle cosine equals 0, ±1/2, or ±1. The only ones of these giving an angle strictly between 0° and 180° are the cosine value 1/2 with the angle 60°, the cosine value –1/2 with the angle 120°, and the cosine value 0 with the angle 90°. The only combination of three of these, allowing multiple use of any of them and summing to 180°, is three 60° angles. Conditions are known in terms of elliptic curves for an integer triangle to have an integer ratio "N" of the circumradius to the inradius. The smallest case, that of the equilateral triangle, has
Equilateral dimension manifold but arbitrarily high equilateral dimension. Equilateral dimension In mathematics, the equilateral dimension of a metric space is the maximum number of points that are all at equal distances from each other. Equilateral dimension has also been called "metric dimension", but the term "metric dimension" also has many other inequivalent usages. The equilateral dimension of a "d"-dimensional Euclidean space is , and the equilateral dimension of a "d"-dimensional vector space with the Chebyshev distance (L norm) is 2. However, the equilateral dimension of a space with the Manhattan distance (L norm) is not known; Kusner's conjecture, named after Robert B.