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Scalar Value

MN_10921447
4-Participant

Scalar Value

Hi everyone.

Im trying to calculate the det of the Jacobian however i keep getting this error.
Just what exactly does "scalar value" mean in mathcad? And more importantly, what can i assign u and v to fix this?
In my problem both u ∈ [0,2π] and v ∈ [0,π] but i dont know how to assign these values in mathcad.

MN_10921447_0-1705671349204.png

ACCEPTED SOLUTION

Accepted Solutions
Cornel
19-Tanzanite
(To:MN_10921447)

Then see this, its your initial Mathcad file. Nothing I changed. You defined in a wrong way the Jacobian matrix...

Cornel_0-1705677802527.png

 

View solution in original post

10 REPLIES 10
Cornel
19-Tanzanite
(To:MN_10921447)

Post your Mathcad file...

Here is an example:

Cornel_0-1705672613720.png

 

 

MN_10921447
4-Participant
(To:Cornel)

Here it is.

Cornel
19-Tanzanite
(To:MN_10921447)

Cornel_0-1705676756965.png

 

Cornel_2-1705676960822.png

 

MN_10921447
4-Participant
(To:Cornel)

Thank you. But can you explain to me why it works for you,but it dosent for me? I dont see any difference at the first glance,other then everything being re arranged.

Cornel
19-Tanzanite
(To:MN_10921447)

Then see this, its your initial Mathcad file. Nothing I changed. You defined in a wrong way the Jacobian matrix...

Cornel_0-1705677802527.png

 

MN_10921447
4-Participant
(To:Cornel)

Oh i see, thank you. The problem is that i dont know how to define partial derivatives in mathcad. Is this also why i cant calculate the surface area of a bohemian dome?

Cornel
19-Tanzanite
(To:MN_10921447)

I am not sure about these formula...
Cornel_0-1705678974357.png

 

Werner_E
25-Diamond I
(To:Cornel)


@Cornel wrote:

Then see this, its your initial Mathcad file. Nothing I changed.

 


Sure you did (apart from correcting the Jacobian definition)!

You change the definition of u and v from ranges to simple scalars. Otherwise you would get the very same error message with the expression in the last line.

 

@MN_10921447 

Apart from the correct definition of the derivatives in the Jacobian, the main "trick" is this:

Werner_E_0-1705678732384.png

Making the determinant a function dependent on r, u and v. Otherwise Prime tries to use the ranges which you defined at the top and fails with the error message you had seen.

 

BTW, I would do without the u- and v-ranges and use CreateMesh for plotting the sphere:

Werner_E_1-1705679766006.png

 

and ... you could create a vector function and use the built-in "Jacob" function:

Werner_E_3-1705680172627.png

Its not necessary to evaluate symbolically, but it sure makes sense, I guess.

 

Cornel
19-Tanzanite
(To:Werner_E)


@Werner_E wrote:

@Cornel wrote:

Then see this, its your initial Mathcad file. Nothing I changed.

 


Sure you did (apart from correcting the Jacobian definition)!

You change the definition of u and v from ranges to simple scalars. Otherwise you would get the very same error message with the expression in the last line.

Yes, true. I didn't notice because from the beginning u and v were changed below in worksheet to scalars by MN guy. If u and v are changed to simple scalars then we can use:

Cornel_0-1705679711859.png


Otherwise, if u and v are range variables then we need to use what also Werner said, DJ(r, u, v):

Cornel_2-1705679454345.png

 

MN_10921447
4-Participant
(To:Werner_E)

Oh, wow,I completely missed those too. Its unreal how much trouble one tiny oversight can create. Also i had no idea you can just do everything with vectors.

Thank you.

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