You mentioned Jacobian could solve.
Then, tabulate row wise those Jacobian 3 values ?

Using rkfixed it do not end. I'll try using your RK23...

Edited by user 07 June 2020 21:04:30(UTC)  | Reason: Not specified

Your last today message has disappeared ???
It happens sometimes ... ?
You can solve for either or all X,Y,Z
from some given conditions [U,V,W].
The problem is ill posed from the onset.
Only trig functions are approximated in radians.
Otherwise, maths are units less.
Some solvers are exclusive of units, others have reserved
variable name. Thus: eradicate units and subscript gyzmas.
Can't find variables, units don't match ...
Can you plot the innermost integral like usual ?
If you can't => there is no project yet.

Hi. Yes, that's what probably it's happen. I try different configurations but can't find none good enough. You can avoid the evaluation at the time of the definition by addint the line command:



Same thing for use DInt function.

My experience for the civil engineering worksheets is that the best choice is use heaviside step for piecewise functions instead inequalities or if and symbolic evaluation for the integrals because in mathcad the numerical procedures for evaluating piecewise integrals are not good. But this can't be done in SMath. Here you can read an example about this problem (there are others about civil eng calculus, but can't fin them): https://community.ptc.co...ction/td-p/124048/page/2

I'm also try to analyze the answer from Martin about using Maxima with heaviside, but again can't get a practical solution, here for the use of solve. Looks that in Maxima, like in Mathcad Prime, there are not correspondence between heaviside in symbolics with the numerical procedures. And this can't be a surprise: heaviside isn't a function, and can't be numerically evaluate like functions.

For a pure numerical application I guess that you need to found a numerical procedure that can handle discontinuities above the integral sign. But for double integrals this could be very slow or inaccurate, like RK23 with a low number of iterations.

Another option could be pass as parameters for the numerical procedure the values of the jumps and integrate between them.

Best regards.
Alvaro.

I don0t know if you got this response, but using Algsys provided in the Máxima plugin I could resolve your problem

What's wrong/missing from native Smath ?

Solve FindRoot [f(x,y) ... g(x,y)].sm (16kb) downloaded 11 time(s).