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25-Diamond I
January 29, 2017
Question

Another bug for the collection

  • January 29, 2017
  • 2 replies
  • 1369 views

I tend to forget a lot of things, so I don't remember if this bug is already known and was reported and discussed here.

Anyway, Mathcads symbolics gives a wrong solution for a simple equation:

but if we use "fully", we get the correct solution, as any value from -1 down is a valid solution:

And also if we replace the square and square root by an absolute value, Mathcads answer is OK:

EDIT: Just noticed:

MuPad knows that

and so we get at least no wrong results if we simplify before we solve

Nevertheless, returning a numerical wrong result in the first place is an absolute no-go in my opinion.

Regards

Werner

2 replies

23-Emerald IV
January 29, 2017

Mathcad 11:

Fortunately not the 0 answer, but I'm not happy with the answer 'x'.

Possibly the Mathcad interface screws up the equation to, and/or the answer from the symbolic processor.

Luc

Werner_E25-Diamond IAuthor
25-Diamond I
January 31, 2017

Thanks for the reply.

So Maple was at least not wrong - just not perfect 😉

> Possibly the Mathcad interface screws up the equation to, and/or the answer from the symbolic processor.

Interesting view and quite possible, I guess. We will never know for sure, though.