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8-Gravel

## Component Derivate for a DGL-System

Hi guys,

I have a quastion. I give you an minimal example. I want to solve a ODE-system with the Radau-Solver. Therefore I need to build the derivate B to component X_2. In the picture you can see, that i can write only X. How can i build this derivate? I know the derivate ist X_1+X_2, but in my real problem i have a big equation-system with many function in another function. So i need a practical solution like  d/dX_2(X_1+X_0*X_2). Can someone help me?

6 REPLIES 6
17-Peridot
(To:fgörlich)

Here's a possible solution - done in M15, but should work in Prime (I think!}.

Unfortunately, when entering B in D it seems you have to list the elements of X explicitly - it doesn't work if you just enter B(X).

Alan

8-Gravel
(To:AlanStevens)

How do you write the red z symbol?

23-Emerald I
(To:fgörlich)

Just type z

When Mathcad looks at the expression it will make the z red with the note "variable is undefined."  That won't impede the calculation.

I think it is a Mathcad Prime problem. It looks likes

The derivate it wrong

23-Emerald I
(To:fgörlich)

Works for me in Prime 3.0:

17-Peridot
(To:Fred_Kohlhepp)

It also works for me in Prime 2 (the only version of Prime that I have):

Alan

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