Let $f : \mathbb{R} \to \mathbb{R}$ be a D4364: Real function such that

(i)	$\mathbb{I}$ is the D370: Set of irrational numbers
(ii)	$I_{\mathbb{I}} : \mathbb{R} \to \{ 0, 1 \}$ is an D41: Indicator function on $\mathbb{R}$ with respect to $\mathbb{I}$
(iii)	\begin{equation} f(x) = x^2 I_{\mathbb{I}} \end{equation}

Then \begin{equation} \{ x \in \mathbb{R} : f \text{ is differentiable at } x \} = \{ 0 \} \end{equation}