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09-16-2012
11:49 AM

09-16-2012
11:49 AM

Derivative of a vector-argument function

Hello!

Could you please help me as I am a newbie in the Mathcad world.

For a university homework, I was trying to solve some simple linear programming tasks (which I did).

However, something goes wrong when I am trying to find the partial derivative of a function which I define as R(y):= cT * y.

And 'c' is a 2D vector.

y is supposed to be from R^2, but I guess, MathCAD doesn't just get it and treats y as a scalar. Am I right? Is there a way to tell MathCAD that y is indeed a 2D vector?

My objective: I want to find d/dy_1 and d/dy_2 of R separately, or at least get a 2D vector containing these derivatives at a particular point.

What should I do? Is there a way to do it without redefining the function?

Please see the attached file for the details.

Thank you so much in advance!

Yours,

P.

4 REPLIES 4

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09-17-2012
03:10 AM

09-17-2012
03:10 AM

Re: Derivative of a vector-argument function

Pavel Kabir wrote:

Is there a way to tell MathCAD that y is indeed a 2D vector?

My objective: I want to find d/dy_1 and d/dy_2 of R separately, or at least get a 2D vector containing these derivatives at a particular point.

What should I do? Is there a way to do it without redefining the function?

Do you really need Mathcad to do this for you? The partial derivatives with respect to y1 and y2 are just the two elements of c here, as R(y) = c1.y1+c2.y2

Alan

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10-21-2012
11:35 PM

10-21-2012
11:35 PM

Re: Derivative of a vector-argument function

I don't use Prime yet, but it works okay in Mathcad 15 if the c vector is specified.

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10-22-2012
06:28 AM

10-22-2012
06:28 AM

Re: Derivative of a vector-argument function

It works fine in Mathcad **Prime 2.0** too:

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10-22-2012
07:59 AM

10-22-2012
07:59 AM

Re: Derivative of a vector-argument function

Here is another possible option that you can try,

Regards

Andy