We denote by $A$ a real square matrix of size 2 and we set, for all $x$ in $\mathbb{R}^2$, $f(x) = Ax$. For $x$ in $\mathbb{R}^2$, express $\operatorname{div}_f(x)$ using only $A$.
We denote by $A$ a real square matrix of size 2 and we set, for all $x$ in $\mathbb{R}^2$, $f(x) = Ax$.
For $x$ in $\mathbb{R}^2$, express $\operatorname{div}_f(x)$ using only $A$.