How can I solve derivative with restrictions/bounds on variable

Hi so essentially I want to solve the derivative of a function. I am currently getting an error as follows: "Unable to find explicit solution"

I am trying to find the variable 'f' which is unknown. I know sigma1 and all other variables are assigned numbers, however I don't know what z is.

I am assuming because my function is a tad complicated, it might be a good idea to restrict the possible values of z. I know z has to be positive and must be less than another L.

Here is a an example of my code thus far.

CC=[1 1 1 1;exp(-w1*L) exp(w1*L) exp(-w2*L) exp(w2*L);-w1 w1 -w2 w2;-w1*exp(-w1*L) w1*exp(w1*L) -w2*exp(-w2*L) w2*exp(w2*L)]^-1*[0;f;0;0];

C1=CC(1); %% This is equal to (5536113736801657*f)/72057594037927936

C2=CC(2);

C3=CC(3);

C4=CC(4);

Sigma1 = -(1/2)*D/A + C1*exp(-w1*z)+C2*exp(w1*z)+ C3*exp(-w2*z)+C4*exp(w2*z);

dSigma1 = diff(Sigma1, z);

solve(dSigma1, z)

Edit: I have tried solve(dSigma1>0,dSigma1<L,z) still not working :/

Answer 1

[Navya Seelam]

Hi,

You can use “assume” function to restrict the values of z

assume(z>0 & z<L); 

Moreover, if you are trying to find variable ‘f’ use solve (dSigma1, f) instead of solve(dSigma1,z)

For more details on “assume” check the link below

https://www.mathworks.com/help/symbolic/assume.html