The Fréchet derivative is in the first Baire class

Eva Kopecká, Luděk Zaj\'ıček

Let $X$ be a normed linear space, $Y$ a Banach space, $G\subset X$ an open set and $f:G\to Y$ a mapping. We show that the Fréchet derivative $f^{\prime }$ of $f$ is of the first Baire clas…