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I'm trying to solve this differential equation. It's not letting me solve the unknowns.
I don't know what I'm doing wrong.
Can u please edit my mathcad prime 3.1?
Thanks
I can't open Prime 3.1 files, just 3.0 format.
So I can't see how you defined the function Theta and what exactly the error message is.
But from the pic you provided I see, that you solve for just five variables but you use six equations which you want to be met! Probably there is no solution and you should rather use "minerr" instead of "find"!?
EDIT: Just realized that, while you wrote about version 3.1, in reality you are using version 3.0.
So a few more errors you have to fix:
- Don't provide a vector as argument in find, but use the variables themselves - comma separated -> Find(t.1,t.2,....t.5)
- Your function definition for z is wrong. This definition calls function F.f and there is an argument missing (n). But I guess the real error is, that F.f should not just have five arguments - no need to provide n. Probably you added it because you got an error as of n being undefined. This error occurs quite often in Prime and is due to wrong auto labeling of the variables done by Prime - very annoying.
- I also consequently change ever variable of integration from t to tau as LucMeekes showed in his answer at your other threat - maybe you should read his answer!! So you see that its not necessary to provide argument t in functions A, B and C.
I have fixed those errors in the attached sheet and now the solve block runs "endless" (I also tried to disable one equation to no avail). I guess the many integrals which have to be calculated for every single iteration step will slow down performance significantly up to the point where it gets unbearable. Every call of F.f will calculate 63 integrals. But a call to theta integrates F.f numerically and that means that F.f is called multiple times (does anybody know know many steps? 100, 1000??) OK lets say 100 steps. So a call to theta calculates 6300 integrals and one single iteration step of the solve block calls theta six times. So we end up with 37800 integrals which have to be calculated for just one step of iteration!!!! Quite time consuming, I guess.
But maybe you have more patience than me and let the sheet run for a longer time - maybe it finishes in finite time.
Otherwise you would find an alternative approach to get what you are after. I haven't looked deep enough at your sheet so I can't help with that.
WE
EDIT: After fixing the t <-> tau problem (never use the variable of integration as a limit of the same integral) the solve block came to an end and it didn't find a solution (all six equations were active). The same result with just the first five equations.
So something with your approach seems to be wrong. BTW, are you sure about the guess values (all =1) ?