Solve equation - "no real roots" result

Solve equation - "no real roots" result - Сообщения

#1 Опубликовано: 27.02.2018 07:10:25
joao sousa

joao sousa

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Howdy,

I am relatively new to SMath (have used Mathcad in the past). I am trying to use SMath to run some engineering calculations. Particularly, I am interested in solving equations - I have used 'solve' function, but always get a "no real roots" message (see file attached).

Can someone help out?

Many thanks in advance!

J
#2 Опубликовано: 27.02.2018 10:44:46
Jean Giraud

Jean Giraud

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I am relatively new to SMath (have used Mathcad in the past). I am trying to use SMath to run some engineering calculations. Particularly, I am interested in solving equations - I have used 'solve' function, but always get a "no real roots" message (see file attached).

Can someone help out?

Many thanks in advance!


Solving means a lot in Engineering works.
No real roots, indicates the solver is ill posed [generally]
Please, don't hesitate to post your problem, there is great expertise in Smath Community.

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#3 Опубликовано: 27.02.2018 13:47:20
Davide Carpi

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Probably are you using the solve(2) function instead of the the solve(4) one (4 arguments, last 2 are the limits of the range where to search the roots)
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#4 Опубликовано: 27.02.2018 14:03:47
joao sousa

joao sousa

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Many thanks ALL for your valuable responses. While I understand what you are saying/showing on your templates, I still haven't managed to figure out what is wrong with the way the solve function is being employed. I have changed the roots range (-100, +100), tried the solve with 4arguments, and still nothing. Is there any chance someone could have a look at the file I have attached originally?

Many thanks,
J
#5 Опубликовано: 27.02.2018 14:40:57
Davide Carpi

Davide Carpi

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Is there any chance someone could have a look at the file I have attached originally?



There aren't attachments in your posts

Цитата

  1. 2018-02-24 19_32_16-Edit post.png

  2. 2018-02-24 19_32_34-Edit post.png

  3. 2018-02-24 19_32_44-Nessun file selezionato..png

  4. 2018-02-24 19_33_24-Edit post.png

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#6 Опубликовано: 27.02.2018 15:37:49
Jean Giraud

Jean Giraud

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Is there any chance someone could have a look at the file I have attached originally?


There is no *.sm document attached !

#7 Опубликовано: 27.02.2018 17:10:19
Jean Giraud

Jean Giraud

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OVNIsolve.PNG
#8 Опубликовано: 02.03.2018 09:46:16
joao sousa

joao sousa

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(Please ignore my post below - I can see the files have been uploaded after all b)

Iff someone could have a look at the .sm file I have attached, I would be very grateful.

Many thanks,
Joao

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Hi ALL,

Many thanks for you interest and responses. Apologies for not having responded but I have been away from the office. I am trying to attach an .sm file, but for some reason this is not working... Any thoughts?

Thanks,
Joao
#9 Опубликовано: 02.03.2018 10:31:55
Jean Giraud

Jean Giraud

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Will be back later during the day
#10 Опубликовано: 02.03.2018 14:16:58
Martin Kraska

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#11 Опубликовано: 03.03.2018 10:59:27
Jean Giraud

Jean Giraud

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Iff someone could have a look at the .sm file I have attached, I would be very grateful.



"NO real roots" from the solve bloc is an absolute pest [not to say stupid].

SolveWisely.PNG

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#12 Опубликовано: 07.03.2018 07:18:35
joao sousa

joao sousa

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Dear ALL,

Many thanks for your incredible support! I am in awe for the depth of knowledge herein displayed.

With regards to your responses, I appreciate the need to make an appropriate substitution to overcome the fact that solve can't handle units in the variable; However, I can´t seem to assign the unit to the variable, within the equation (apologies for being thick). I've tried typing x'm, tried using ctrl+w to assign meters unit to x, but still haven't managed to make it work. A bit frustrating... If anyone could be so kind to shed some light here, that would be greatly appreciated.

Many thanks,
J
#13 Опубликовано: 07.03.2018 13:08:03
Martin Kraska

Martin Kraska

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Dear ALL,

Many thanks for your incredible support! I am in awe for the depth of knowledge herein displayed.

With regards to your responses, I appreciate the need to make an appropriate substitution to overcome the fact that solve can't handle units in the variable; However, I can´t seem to assign the unit to the variable, within the equation (apologies for being thick). I've tried typing x'm, tried using ctrl+w to assign meters unit to x, but still haven't managed to make it work. A bit frustrating... If anyone could be so kind to shed some light here, that would be greatly appreciated.

Many thanks,
J





Type x*'m or x* and then insert the unit from the dialog into the empty placeholder in the right of the multiplication dot.

Multiplication operators in front of units aren't shown.
Martin Kraska Pre-configured portable distribution of SMath Studio: https://en.smath.info/wiki/SMath%20with%20Plugins.ashx
#14 Опубликовано: 08.03.2018 01:50:22
Jean Giraud

Jean Giraud

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Many thanks for your incredible support! I am in awe for the depth of knowledge herein displayed.

With regards to your responses, I appreciate the need to make an appropriate substitution to overcome the fact that solve can't handle units in the variable; However, I can´t seem to assign the unit to the variable, within the equation (apologies for being thick). I've tried typing x'm, tried using ctrl w to assign meters unit to x, but still haven't managed to make it work. A bit frustrating... If anyone could be so kind to shed some light here, that would be greatly appreciated.



You are debating with the Unit SI as implemented in Smath [Mathcad ...]
You may pacify your soul on several counts:
1. maths are unit less
2. ISO standards have their own units [most generally from SI derived units].
... therefore converting automatically bar in Pa ... etc.
3. Engineering formulas are constructed around the appropriate Units
... therefore no need to freak them more.
4. Consider this example: you have a formula, from which you can directly/indirectly
compute the arc length ... in what SI units Watson ???
... simple Sherlook ... in "UnitGraphic" that you can meter in year-light/micrometer ...
5. How did we do in the age of the slide rule, in the age of paper/pencil/log tables ?
6. Was Sputnik launched from SI unit software ?
#15 Опубликовано: 28.12.2019 22:19:53
jdoe1

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I'm having a similar problem, it works on wolfram and symbolab, but not in Smath.



#16 Опубликовано: 28.12.2019 23:32:16
Jean Giraud

Jean Giraud

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it works on wolfram and symbolab, but not in Smath.


Always plot first ...

Solve -Plot.PNG
#17 Опубликовано: 29.12.2019 21:09:09
jdoe1

jdoe1

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it works on wolfram and symbolab, but not in Smath.


Always plot first ...

Solve -Plot.PNG



I somehow missed the option to use the 2nd solve function with root limit, but I didn't need a plot for this, so I used it in one line and everything worked out fine.

I can't click the thank button, so thanks.
#18 Опубликовано: 29.12.2019 23:01:26
Jean Giraud

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I somehow missed the option to use the 2nd solve function with root limit, but I didn't need a plot for this, so I used it in one line and everything worked out fine.


If you don't plot, you will soon hit the wall.
That will help set the limits.
When applicable, "implicit roots" is often + accurate.

roots.PNG
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