Variable is undefined error - given/find function

[ps-7]

Hi Everyone,

I read the discussion about this error and tried to solve it with method from this link: This variable is undefined error when using Given/Find function, why?
It didn't help me. So I'd like to ask you for help. I really can't find the problem on my own.

I will be grateful for any advice.

Piotr

[StuartBruff]

Piotr S wrote:

Hi Everyone,

I read the discussion about this error and tried to solve it with method from this link: This variable is undefined error when using Given/Find function, why?
It didn't help me. So I'd like to ask you for help. I really can't find the problem on my own.

Hi Piotr,

In this case, I think it's because there is no exact solution, so Find will return an error ... which, unhelpfully, is an undefined variable error.

Try Minerr instead, then look at the results to see if they're acceptable / make sense.

Stuart

[Werner_E]

Thats strange. I get a solution with find (the same as Stuarts) when using symbolic evaluation.

BTW, the problem with the numeric eval has somehow to do with the units. Getting rid of the units enables the system to solve numerically, too.

[AlanStevens · Accepted solution]

Because it is linear in the R's you can do it as below:

Alan

[ps-7]

Thank you for your response. I think if there was no exact solution for these equations AlanSteven's method wouldn't have worked. Both methods provide proper solution. I need to read more about minerr function, because I haven't used it before.

However, it would be easier if Matchad could return information about the problem, not only undefined variable error.

Appreciate your help

Piotr