Yes, the matrix inverses are too complicated to do symbolically. So, I suppose that you have a differential system which you will solve for the ten functions alpha(t), beta(t), psi[1..4](t), and phi[1..4](t), right? And for that you are going to use dsolve(..., numeric), right?

So, we can consider your complicated expression as a matrix-valued function of t, right? And you only need it evaluated for numeric values of t, right?

If the answer to these questions is "yes", then it will be possible to modify your code so that it very quickly evaluates the matrix expression for any numeric t, although I have some mild concerns about numeric stability.

@Bendesarts I can download the file now. The problem was due to a bug in the recent MaplePrimes software update. You did not do anything wrong. Sorry for the confusion and hassle.

@gkokovidis Yes, I have noticed that pages load significantly faster. I was addressing specifically the issue of the speed with which updates appear in the right sidebar column: "Active Conversations", "Recent Posts", etc. I have not noticed an improvement in that. Indeed, there was a Question from two days ago that I answered 8 hours ago which still has not re-appeared in "Active Conversations".

I was able to login after deleting my MaplePrimes cookies.

A new bug I just encountered: While editing this Comment, I pressed Submit. The page refreshes, but it doesn't take me out of the editor. But the edited version is posted anyway.

There are syntax errors in your PDE. Would you please try uploading it again? Or upload a worksheet.

@Bendesarts I tried the links in Markiyan's Reply and yours and I just get "Error 404---File not found". I've tried in three web browsers: Internet Explorer, Firefox, and Pale Moon. This may be related to the recent MaplePrimes software update.

The link in your Question does not work. It is asking for login credentials. Please upload a Maple worksheet instead.

@bunmipopoola Preben did respond, but you didn't see it because of a bug in MaplePrimes. Because of the recent software update to MaplePrimes, you may need to refresh the webpage to see responses. In Internet Explorer, I need to refresh every page every time I visit it.

@Kitonum This model seems rather unlikely to me. The data are nondecreasing, but the model has a local maximum at x=1.83---just to the right of the end of the dataset. The marginal improvement in the fit that you get from the extra term (as measured by the first value returned by DataFit) seems too small to justify using the extra term.

@Adri van der Meer That should be

plot([X(t), Z(X(t)), t=0..10], numpoints= 200, color= blue, legend= "z(x)");

A problem is that some of your first coordinates are repeated. Can you get another digit of accuracy so that that is not the case?

It is not really working in IE either, but it's working better than in Firefox.

It's not really working in IE either, but it's working better than in Firefox.

@NoThik Only the first vector returned by IntegerLinearSolve satisfies the equation A.X=B. The remaining vectors are a basis for the nullspace of A.

@NoThik Only the first vector returned by IntegerLinearSolve satisfies the equation A.X=B. The remaining vectors are a basis for the nullspace of A.

@Alexander zhang I'm still thinking about it. I need to refresh my knowledge of surface integrals.