I want to get the gradient of a parameter. For example:

parameter: `t`

`A = [[cos(t), -sin(t)], [sin(t), cos(t)]]`

`x = [[1], [10]]`

`y = A x`

`z = ||y||^2`

I want to know how to code to get the gradient of `theta`

where loss function is `z`

.

```
theta = torch.tensor(1.0, dtype=torch.float32, requires_grad=True)
A = torch.Tensor([
[torch.sin(theta), torch.cos(theta)],
[torch.tan(theta), torch.exp(theta)]
])
x = torch.tensor([[1], [10]], dtype=torch.float32)
y = torch.matmul(A, x)
z = torch.matmul(y.T, y)
```

But I found `A.requires_grad`

is `False`

, and the same to `z`

.