Hi
I am reposting this as I didn't get any answer the last time. I am working
on discret wave equations and I need a symbolic expression for
$\frac{d^2 p(x,t)}{dt^2} - G_{\bar{x}\bar{x}}^T((1+2\epsilon) p(x,t)) -
G_{\bar{z}\bar{z}}^T(\sqrt{(1+2\delta)} r(x,t)) =q$
where
$G_{\bar{x}\bar{x}} & = cos(\theta)^2 \frac{d^2}{dx^2} + sin(\theta)^2
\frac{d^2}{dz^2} - sin(2\theta) \frac{d^2}{dx dz} \\
G_{\bar{z}\bar{z}} & = sin(\theta)^2 \frac{d^2}{dx^2} + cos(\theta)^2
\frac{d^2}{dz^2} +sin(2\theta) \frac{d^2}{dx dz} \\ $
however as_finite_diff doesn't allow any cross derivatives (d/dxdy) even so
the documentation says it does (it only does if you define it and then only
take d/dx or d/dy)
The second problem is to take derivatives of product. It shouldn't be a
problem as this is just another function but it doesn't work neither.
thank you
mathias louboutin
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