Optimal bicentered form (Q1397890)

Centered forms are well-known inclusion functions for real functions. \textit{E. Baumann} [BIT 28, No. 1, 80-87 (1988; Zbl 0641.65043)] established an optimal developing point for the construction of centered forms. Originally, he has two such points, one for the upper boundary and one for the lower boundary of the inclusion function. Now, the author brings these two points into a ``symmetric'' form for getting a closed expression and creats thus the optimal bicentered form. An estimation of the related excess-width is also given.