Eine komplexe Ungleichung aus elementarer Sicht. (A complex inequality from an elementary point of view) (Q919126)
From MaRDI portal
 | This is the item page for this Wikibase entity, intended for internal use and editing purposes. Please use this page instead for the normal view: Eine komplexe Ungleichung aus elementarer Sicht. (A complex inequality from an elementary point of view) |
scientific article; zbMATH DE number 4159019
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | Eine komplexe Ungleichung aus elementarer Sicht. (A complex inequality from an elementary point of view) |
scientific article; zbMATH DE number 4159019 |
Statements
Eine komplexe Ungleichung aus elementarer Sicht. (A complex inequality from an elementary point of view) (English)
0 references
1988
0 references
In operator theory, it is known and used that if \[ f(z_ 1,z_ 2)=1+2(z_ 1+z_ 2)+(z_ 1-z_ 2)^ 2\text{ with } z_ 1,z_ 2\in {\mathbb{C}} \] and \(| z_ 1| =| z_ 2| =1\) then \(| f(z_ 1,z_ 2)| \leq 5\). The author proves the inequality above elementarily. In fact, he reduces the problem to an elementary geometric problem.
0 references
