## 67 Reputation

18 years, 311 days

## Non-commutative Operations...

Maple
I'm glad to see the dot operator and I'm trying to get around some limitations since it doesn't understand general matrices and vectors. Consider the expression T(g(a)).h(a). In my case, T is a transpose operation and a is a vector. I'm trying to differentiate it with respect to a. The general derivative is of the form, T(h(a)).diff(g(a),a) + T(g(a)).diff(h(a),a). My question is how to get Maple to understand how to apply this particular derivative rule. If I just blindly apply the derivative, I get the second term fine, but the first term is not in a useful form. Basically, I need to tell diff how to carry out the product rule for these non-commutative terms.

## General Volume and Surface Integrals...

Maple
I've been trying figure out how to code up arbitrary volume and surface integrals in Maple. I know that Maple has the VectorCalculus package but there doesn't appear to be a way to specify a volume integral (where the infinitesimal is dV). Also, there doesn't seem to be a way to specify a surface integral without defining the surface in advance (i.e., integrate over S with an infinitesimal of dS). In both cases, I'd like to have general integrals where I can specify the bounds at a later time (e.g., inert integrals). I know that there is the triple integrals in the student package but they aren't the same as a volume integral.

## Extracting derivatives of functions from...

Maple
Does anybody know of a way to extract derivatives of a specified function from an expression? For example, if I have the expression, int(D(F)(x,t,y(x,t),diff(y(x,t),x),diff(y(x,t),t),diff(diff(y(x,t),t),x))*diff(diff(yv(x,t),t),x),t = t1 .. t2); I'd like to be able to get the derivatives of yv(x,t) which in this case would be, diff(diff(yv(x,t),t),x). I ask because I'm trying to systematically integrate a set of expressions by parts where I know that the dv term always contains a certain function's derivatives and I can stop integrating by parts once I have just the function.
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