Real analytic function
= Real analytic function
{wiki}
= Real analytic
{synonym}
A function $f$ is real analytic at $y$ when its <Taylor series>
$$
\sum_{\alpha\in\mathbb N^n}\frac{D^\alpha f(y)}{\alpha!}(x-y)^\alpha
$$
converges to $f(x)$ throughout some <neighborhood> of $y$.