# linear algebra derivative expressions

How do I differentiate $\mathbf{y}=\mathbf{A}\mathbf{x}$ symbolically in sagemath with respect to the vector $\mathbf{x}$? The result is obviously $\mathbf{A}$. Similarly, I would like to be able to calculate the derivative of the quadratic form $\alpha=\mathbf{x}'\mathbf{A}\mathbf{x}$. I would need these calculations in a more complex setting.

I started off with sympy as follows

```
from sympy import *
n=7
A = MatrixSymbol('A', n, n)
x = MatrixSymbol('x', n, 1)
```

Or is there a different library from sympy available for such a problem?