Recently, Dekster introduced a new angle measure for Minkowski spaces according to which the total angular measure τ around a point in a two-dimensional Minkowski space need not be 2π. In this paper, we shall show that while τ need not be 2π, τ always lies between √ 2π and 8. (2000): Primary 51B20, 52A38.
Mathematics Subject ClassificationLet B be a centrally symmetric compact convex subset of E 2 with nonempty interior, and let M denote the two-dimensional Minkowski space for which B is the closed unit disk.Dekster's angle measure in M, defined in [1], is given bywhere ϕ denotes the (oriented) Euclidean angles between the positive x−axis and the ray R ϕ with initial point O, r (ϕ) is the Euclidean distance between O and the point P ϕ on the boundary of B lying along the ray R ϕ , and b (ϕ) equals the Euclidean distance between the two supporting lines parallel to the ray R ϕ . It is immediate that for every ϕ, 1. P ϕ is the point (r(ϕ) cos ϕ, r(ϕ) sin ϕ).
We have4. If B is the Euclidean unit disk, then r (ϕ) = 1 and b (ϕ) = 2 for all ϕ, and so M (α, β) = β − α.
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