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Köbe's One-Fourth Theorem

If f is a schlicht function and D(z_0,r) is the open disk of radius r centered at z_0, then

f(D(0,1)) superset= D(0,1/4),

where superset= denotes a (not necessarily proper) superset (Krantz 1999, p. 150).

See also

Köbe Function, Schlicht Function

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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: Hermann, p. 24, 1983.

Referenced on Wolfram|Alpha

Köbe's One-Fourth Theorem

Cite this as:

Weisstein, Eric W. "Köbe's One-Fourth Theorem." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/KoebesOne-FourthTheorem.html

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