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J
JB_107454694-Participant
4-Participant
July 26, 2023
Solved

Minimise value in solve block

  • July 26, 2023
  • 2 replies
  • 2690 views

Hi,

 

I am looking to find a minimum value of 'ey' within a solve block based on a set of equations, which otherwise give a circular reference.

So far I cannot manage for the solve block to give me an answer and I was looking for some help.

 

Screenshot of problem:

JB_10745469_0-1690379907714.png

Using PTC Mathcad Prime 8.0.0.0

 

Thanks,

JB

Best answer by LucMeekes

In Prime 7 I get an error message, that it can't find a solution.

A little more tweaking:

LucMeekes_1-1690402563066.png

gives:

LucMeekes_0-1690402670824.png

Success!
Luc

2 replies

T
21-Topaz II
terryhendicott21-Topaz II
21-Topaz II
July 26, 2023

Hi,

 

Only have version 9.

Take all the functions outside the solve block

Define a function for ey the function to minimise.

Set ey as the thing to minimise

Capture.JPG

 

Capture2.JPG

L
LucMeekes23-Emerald IVAnswer
23-Emerald IV
July 26, 2023

In Prime 7 I get an error message, that it can't find a solution.

A little more tweaking:

LucMeekes_1-1690402563066.png

gives:

LucMeekes_0-1690402670824.png

Success!
Luc

    J
    JB_107454694-ParticipantAuthor
    4-Participant
    July 28, 2023

    Thanks for the solution @LucMeekes and thanks to the other replies.

     

    I did make it a little confusing when I set the solver to solve for 'XYZ' - this was just a random term to solve for a minimum value of 'ey' but did not fully realise I had 'X', 'Y' and 'Z' already within the equations!

     

    Also, as 'X' was a fixed value, I managed to remove it from within the brackets of the beta equations.

    W
    Werner_E25-Diamond I
    25-Diamond I
    July 26, 2023

    It looks like you will have to supply additional information!

     

    Which quantity should be as small as possible? Is it e.y as Terry had supposed or is it beta.ey as Luc had?

    Also necessary: Which of the variables you defined may be varied to achieve this goal? Terry varied X,Y and Z.end while Luc varied e.y.

     

    Generally you have to know that the quantity you would like to minimize must be a function depending on the quantities you are willing to vary to achieve this goal. You can't minimize a variable.

    T
    21-Topaz II
    terryhendicott21-Topaz II
    21-Topaz II
    July 27, 2023

    terryhendicott_0-1690460215778.png

     

    W
    Werner_E25-Diamond I
    25-Diamond I
    July 27, 2023
    @terryhendicott wrote:

    terryhendicott_0-1690460215778.png

     

    yes, I saw this. But he defined a guess value for e.y which normally means that e.y is the value to vary and even if he saw e.y as function to minimize its absolutely not clear to me which variables should be varied to achieve this goal.

    Anyway, a timely feedback from the questioner on the two suggestions already given and further clarification would be quite appropriate and necessary in my opinion.

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