AbstractJack’s Lemma says that if f(z) is regular in the disc $$|z|\le r$$
|
z
|
≤
r
, $$f(0)=0$$
f
(
0
)
=
0
, and |f(z)| assumes its maximum at $$z_0$$
z
0
on the circle $$|z|=r$$
|
z
|
=
r
, then $$z_0f'(z)_0/f(z_0)\ge 1$$
z
0
f
′
(
z
)
0
/
f
(
z
0
)
≥
1
. This Lemma was generalized in several directions. In this paper we consider an improvement of some first author’s results of this type.
On an extension of Nunokawa’s lemma
