We consider the function $f$ defined by: $\forall (x,y) \in \mathbb{R}^2,\ f(x,y) = \frac{1}{1+x^2+y^2}$.
Is the function $\frac{\partial f}{\partial x}$ in $\mathcal{B}_2$?
We consider the function $f$ defined by: $\forall (x,y) \in \mathbb{R}^2,\ f(x,y) = \frac{1}{1+x^2+y^2}$.

Is the function $\frac{\partial f}{\partial x}$ in $\mathcal{B}_2$?