Köbe's one-fourth theorem states that if 
is a schlicht function
and 
is the open disk of radius 
centered at 
, then
 |
where 
denotes a (not necessarily proper) superset (Krantz
1999, p. 150).
Köbe's One-Fourth Theorem
See also
Köbe Function, Schlicht FunctionExplore with Wolfram|Alpha
References
Krantz, S. G. "The Köbe 1/4 Theorem." §12.1.5 in Handbook of Complex Variables. Boston, MA: Birkhäuser, pp. 150-151, 1999.Le Lionnais, F. Les nombres remarquables. Paris, France: Hermann, p. 24, 1983.Referenced on Wolfram|Alpha
Köbe's One-Fourth TheoremCite this as:
Weisstein, Eric W. "Köbe's One-Fourth Theorem." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/KoebesOne-FourthTheorem.html