For any nonzero elements x,y in a normed space X, the angular and
skew-angular distance is respectively defined by ?[x,y] = ||x/||x|| - y/||y||||
and ?[x,y] = ||x/||y|| - y/||x||||. Also inequality ? ? ? characterizes inner
product spaces. Operator version of ? p has been studied by Pecaric,
Rajic, and Saito, Tominaga, and Zou et al. In this paper, we study the
operator version of p-angular distance ?p by using Douglas? lemma. We also
prove that the operator version of inequality ? p ? ?p holds for normal and
double commute operators. Some examples are presented to show essentiality
of these conditions.