solver function

[SS_14365390]

Hello!!

i am kind of new to the program and I have researched but still can not find the answer. I tried to create a solve block where I can get the final reult of a variable H_2 but it does not work.

I upload a PDF of the problem. I believe is not difficult but perhaps I am missing something

[Werner_E]

Whenever possible its always better to upload the worksheet itself rather than a static picture or pdf.

And your pdf does not shoe any attempts of a solve block or the like. Its not clear which equation you want to solve for variable H2.

Maybe its the equation s2-Delta_s2=s0 ????

So please upload your worksheet and explain in more detail what you are trying to achieve.

BTW, instead of a solve block with "find" you can also use the "root" function in one of its two flavors.

[SS_14365390]

Thank you for your reply. Yes, the equation is s2-Delta_s2=s0. So its an equation with 2 incognitas (H_2 and S_o) so I assume I have to iterate to fin H_2 until it converges.

I am going to check the root function and see.

[LucMeekes]

"so I assume I have to iterate":  No you don't.

You need to correct one error:  There's a q_2 in one expression which probably should be a q₂.

You should refrain from evaluating definitions. That is: remove the  =  at the end of the definitions of s₂ and ds_2.

You should write s₂ and ds₂ as functions of H₂, so you get:

and

And bear in mind that s₂ also appears in the definition of ds₂, so there it is also a function of H₂.

Then finally you can solve:

s₀ - s₂(H₂) - ds₂(H₂) 

as the function to solve for H₂ in the root(), for any value of s₀.

Or you could (try to) symbolically solve H₂ as a function of s₀.:

(Make sure that you type a bold equals for this equation.)

Success!
Luc

[Werner_E · Accepted solution]

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@SS_14365390 wrote:

Thank you for your reply. Yes, the equation is s2-Delta_s2=s0. So its an equation with 2 incognitas (H_2 and S_o) s

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If you really have TWO unknowns you would also need two equations, not just one! So what would be the second equation in H_2 and s_0 ??

But in case s_0 is known (as to seem to be the is the case in your PDF)

you could  define functions as explained by Luc

and use them either with the "root" function or in a solve block with "find":

BTW, I would not recommend using the symbolic “solve” facility if the only goal is to find a numerical solution. In this specific case, it could also fail due to the integral.

EDIT: Gave it a try, and  - yes - "no solution found":

Prime 11 sheet attached

[SS_14365390]

Thank you all. It worked!! 🙂

however, now I have a problem with finding for another state H3. I got the formulas from university presentation and it says is not converging to a solution.