Simplify sin(n*pi)

[RichardJ]

Why won't

sin(n*pi) assume n=integer

simplify? Even this won't simplify:

sin(n*pi) assume n=integer, n=real

(I believe integers only include the reals anyway, but it was worth a try).

Am I missing something, or is this a bug?

Richard

[Luc_Meekes-disa]

Guess it's a Mupad feature, it does simplify to 0 in Mcad 11.2.

Luc

[RichardJ]

It never even occurred to me to check what 11 did, since "integer" is not a documented modifier.

But that does confirm it's a bug, and not just me being dense. Thanks.

Richard

[ptc-1368288]

On 11/19/2009 7:06:17 PM, rijackson wrote:
>Why won't

sin(n*pi) assume
>n=integer

simplify? Even this
>won't simplify:

sin(n*pi)
>assume n=integer, n=real

(I
>believe integers only include
>the reals anyway, but it was
>worth a try).

Am I missing
>something, or is this a bug ?<<br>
Richard
______________________________

Surely you forgot that for all � n = integer
sin(n*pi) simplifies to 0.
MuPad didn't care rectifying this lack of knowledge base.

jmG

[alnstevens]

Gives zero for me! (M14, M020)

stv

[ptc-1368288]

On 11/21/2009 4:33:57 AM, stv wrote:
>Gives zero for me! (M14, M020)
>
>stv
_______________________________

Obviously as I have explained, last night. The detail is that if such a case would arrive in numerical calculations "and if" the total accuracy is needed for the suite of the project, the user must then use 0 instead of the numerical evaluation. Numerically, sin(n*pi) will be displayed 0 but not necessarily 0 in the floating point. It could be 0 but we don't know what kind of numerical approximation the Pentium is running.
In other words: the numerical sin(n*pi) may/mayNOT = 0.

jmG

[RichardJ]

Yes, with the simplify keyword added that's true. I'm surprised I didn't notice that! IMHO it should work without the simplify keyword though.

Richard

[ptc-1368288]

On 11/21/2009 10:20:41 AM, rijackson wrote:
>Yes, with the simplify keyword
>added that's true. I'm
>surprised I didn't notice
>that! IMHO it should work
>without the simplify keyword
>though.
>
>Richard
_____________________________

Yes Richard, it should work w/o the keyword "simplify". A left over from designers ? or something unexplained ? Just trying to think if it has some reason with the n root of unity. Or other symbolic reason ... actually, I have 4 symbolic representation of sin(x), two are well known. Anything to do with Fourier transform.

An academic curiosity ?
Any other mathematical justification ?

jmG

[alnstevens]

On 11/21/2009 10:20:41 AM, rijackson wrote:
>Yes, with the simplify keyword
>added that's true. I'm
>surprised I didn't notice
>that! IMHO it should work
>without the simplify keyword
>though.
>
>Richard

Even M11 sometimes requires the simplify keyword when you'd expect it not to - see sin^2 + cos^2, for example.

stv

[ptc-1368288]

On 11/23/2009 6:40:27 AM, stv wrote:
...
>Even M11 sometimes requires the simplify
>keyword when you'd expect it not to -
>see sin^2 + cos^2, for example.
>
>stv
_______________________________

The simplify is not needed from knowledge base. The expanded form is more than needed for vector construct (not to be demonstrated).



jmG

[RichardJ]

On 11/23/2009 6:40:27 AM, stv wrote:

>Even M11 sometimes requires the simplify
>keyword when you'd expect it not to -

Yes, that's true. It would be so much easier if it just did exactly what I think it should do 🙂

Richard

[mzeftel]

I'll add to the feature requests for symbolics, to not have such rigid requirements for keywords. I don't know what's possible in that regards.

Mona

[ptc-1368288]

On 12/3/2009 2:01:57 PM, MonaZ wrote:
>I'll add to the feature
>requests for symbolics, to not
>have such rigid requirements
>for keywords. I don't know
>what's possible in that
>regards.
>
>Mona
_______________________________

"Simplify sin(n*pi)"

I have explained one way. The designers are invited to read more as noted. For the others, only one bug as noted in red. For the reported blue bug, no image was passed to appreciate and compare. So, for that one (blue), there is no bug, just mishandling.



Jean