A finite dimensional normed linear space is usually called a
Minkowski space. Suppose that for the parameter $t$ changing from 0 to 1 two points $p_1(t)$ and $p_2(t)$ traverse the boundary of a convex body $K$ in a Minkowski plane with respect to counterclockwise and clockwise orientation, respectively, and that they do not coincide for each $t.$ We prove that $K$ is of constant Minkowskian width if and only if the Minkowskian distance between $p_1(t)$ and $p_2(t)$ is a unimodal function of $t$ for each possible choice of the functions $p_1(t)$ and $p_2(t).$ Furthermore, we give an appropriate extension of the ``only if'' part of this result to higher dimensional Minkowski spaces.
Keywords:
body of constant (Minkowskian) width, Minkowski space, monotonicity lemma