Community Tip - Did you get called away in the middle of writing a post? Don't worry you can find your unfinished post later in the Drafts section of your profile page. X
I find the answer from this community.
I find the answers.
As you have found out for yourself, the new symbolic module is clearly inferior to the old legacy muPad (and muPad was already a big step backwards compared to Maple, which was used earlier). Conclusion: Use the legacy symbolic for symbolic calculations as long as it is still possible and then switch to a more powerful software later.
With muPad what you tried is no problem:
But even with the new catastrophe there are possibilities:
It seems like it's "just" the arg-function, which the new Symbolic can't handle properly:
The "unknown error: index_out_of_range" is rather strange and I would call it a bug.
Needless to say that the legacy symbolic handles the expression without problems:
Good old Mathcad 11:
Success!
Luc