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Problem solving a simplle equation with sin ?

ptc-1739038
5-Regular Member

Problem solving a simplle equation with sin ?

A simple problem wich worked fin in Prime 6 and doesnt in Prime 7.

In the first line, a simple equation is solved (it's a linear equation!) - all works fine ...

Then some constants where defined and a equation of the same type is to be solved => won't work, after a very long time there is some message, that there is not enough memory (again, to solve a linear equation!!).
If one first calculates the left side of the equation, it works ....
Whats wrong here? Prime error or mine .....

ptc1739038_0-1642168167446.png

 

 

18 REPLIES 18
ptc-1739038
5-Regular Member
(To:ptc-1739038)

ptc1739038_0-1642168250666.png

 

It appears you need to add the "deg" unit identifier to your angles and it will work:

ChrisKaswer_0-1642168621332.png

 

ptc-1739038
5-Regular Member
(To:ChrisKaswer)

Thanks ….
But it should work also in the other form ….

In general it works better to reverse the process. First solve the equation, then fill in the numbers:

LucMeekes_0-1642169607764.png

Note that Prime symbolics doesn't normally work with units...

 

Success!
Luc

ptc-1739038
5-Regular Member
(To:LucMeekes)

Thanks, but you cannot tell pupills of age 15 to define a function with 3 variables

That may be true, I can't remember if I was up to such math at that age.

But I'm sure you can tell them to NEVER add a unit to the symbol of a variable. Units should only be added to values...

 

Success!

Luc


@ptc-1739038 wrote:

A simple problem wich worked fin in Prime 6 and doesnt in Prime 7.

No, thats wrong. What you tried doesn't work in Prime 6 either!

Main reason is that the unit deg is only known to the numeric, but not to the symbolic engine.

You may (re)define "deg" yourself to make it known to the symbolics,too, and what you tried to do will work OK

Werner_E_1-1642180417397.png

!!!BUT ..... what you did is a mathematical and pedagogical disaster! An absolute no-go! The same applies as Luc already said to your approach of adding a unit to an already defined variable. Never do so!
You define an angle to be 85.2 but you mean 85.2 °!! Thats a big difference! Defining alpha to be 85.2 means it to be 85.2 radian per definition.

So the correct way sure is to define the variables with their correct units and while you are doing this you may also assign a unit to l which obviously should be a length:

Werner_E_2-1642180642710.png

You may also use the numeric "root" function or a (numeric) solve block to find x, but what was said concerning variables and units still applies here, too, of course.

 

ptc-1739038
5-Regular Member
(To:Werner_E)

" ..... what you did is a mathematical and pedagogical disaster! "
Nice forum, one ask for help and gets insulted ... but the joke is on you, this is the work of a student, so basically you shamed a 15 year old. Kudos.
"No, thats wrong. What you tried doesn't work in Prime 6 either!"
I think it has, and most of the time it works in Prime 7 to. I think thats why they used it in the first example. Here a working one

ptc1739038_0-1642316839222.png

And how a missing unit can cause the symbolic engine into an "Memory Overflow Error" is strange ...



ptc-1739038
5-Regular Member
(To:ptc-1739038)

The "solution" with all the units doesnt work here either:

ptc1739038_1-1642317682569.png

What a the correct setttings here:

ptc1739038_2-1642317769454.png

I tried it with units on and units off in symbolic math -> no change in behavior ...

 

 


@ptc-1739038 wrote:

" ..... what you did is a mathematical and pedagogical disaster! "
Nice forum, one ask for help and gets insulted ... but the joke is on you, this is the work of a student, so basically you shamed a 15 year old. Kudos.

I had no intention of insulting anyone and I don't see that anyone would have been insulted. You were told that you did something wrong and up to your last post we had to assume that is was your own attempt as a teacher you was showing. Furthermore you were told how to do it better.

I agree that the error of the symbolic engine is rather strange and should not pop up even if you setup the calc as you (or your pupil) did initially.

And concerning your follow up posting, I also can't see why and how the approach with the attached units fails at your side - but then, its hard to debug  just a picture. It may help if you attach the worksheet.

 

Find attached a worksheet with a working version of the problem (at least it works for me in Prime 5 and Prime 6 - I have no P7 installed)

Werner_E_0-1642350754252.png

 


@ptc-1739038 wrote:

" ..... what you did is a mathematical and pedagogical disaster! "
Nice forum, one ask for help and gets insulted ... but the joke is on you, this is the work of a student, so basically you shamed a 15 year old. Kudos.


It is a nice forum and people usually do get help. I didn't read it as insulting, merely terse and to the point, and a comment on the method, not the individual.

 

If you'd added the information about the work being that of a 15-ys old student, then I'm confident that Werner would have phrased it differently.  However, without that information, the natural assumption is that an adult with some experience is the author, and has learned to accept a range of styles without feeling threatened or belittled.

 

I'm also confident that there are better ways to have made your point without unmistakeably attacking somebody who has voluntarily given their time to help you. 

 

Stuart


@ptc-1739038 wrote:

"No, thats wrong. What you tried doesn't work in Prime 6 either!"
I think it has, and most of the time it works in Prime 7 to. I think thats why they used it in the first example. Here a working one

ptc1739038_0-1642316839222.png

And how a missing unit can cause the symbolic engine into an "Memory Overflow Error" is strange ...

 


I'll second Werner's request for you to please post a complete worksheet.  It's often difficult, if not impossible, to look at a problem from just the picture, especially when not all of the variables are defined and the low resolution makes it difficult to interpret symbols (even when zoomed).  Pictures are very useful but they don't tell the whole story.

 

Stuart 

sinsin.png


@ValeryOchkov wrote:

sinsin.png


Yes, thats what Luc suggested in his first reply to solve the equation symbolically. But to make it useful to get a numeric result later it would mean that you have to turn it in a function of three arguments and this idea was rejected by the OP because he felt that this approach would not be appropriate for his students/pupils.

Sure the symbolic SHOULD be able to provide a solution for this simple equation even when the variables are already assigned values and even with the approach which was posted initially (adding the degree "unit" to the variable in the equation). For reasons I can't explain the symbolic sometimes chokes on this equation and while playing around (in Prime 6) I also experienced the problem that the symbolic will run "endless" without returning an solution. I would call it a strange bug (and it has nothing to do with the new symbolic engine, it also happened when I used the legacy engine).

ptc-1739038
5-Regular Member
(To:Werner_E)

Support wanted to know if this is solved ...

In my eyes, this is a bug. If the shown input works for one example and leads to an (almost) endless calculation with the same syntax in the other, this can only be a bug. Either it does not work at all or it does ...
And: nothing is defined before the two examples. Both were done in a new worksheet of their own.


@ptc-1739038 wrote:

Support wanted to know if this is solved ...

In my eyes, this is a bug. If the shown input works for one example and leads to an (almost) endless calculation with the same syntax in the other, this can only be a bug. Either it does not work at all or it does ...
And: nothing is defined before the two examples. Both were done in a new worksheet of their own.


I think you have two options:

 

1.  It's a bug and the thread can't be marked solved until it's fixed.

 

2. You have confirmation that it's a bug.  As this answers your original question, you can mark an answer as the solution, thus closing the thread.

 

Either way, you can raise a bug report linking to this thread.

 

I'd probably go for option 2, as it's factually correct, but add a new message confirming it's a bug and, ideally, giving your problem report reference. This stops debate with support whilst still letting people know the underlying problem is still there.  

 

Stuart   

ptc-1739038
5-Regular Member
(To:StuartBruff)

Where do I report this as a bug ?

VladimirN
23-Emerald IV
(To:ptc-1739038)

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