03-22-2018, 07:35 PM (This post was last modified: 03-22-2018 08:15 PM by Darno.)
Post: #1
 Darno Junior Member Posts: 11 Joined: Mar 2018

Apparently I am not allowed to upload images... Or I do not know how to do it in this forum!

The expression is complicated to write without mathematical symbols: involves third root radicals and exponent. When I input it I get the message "temporary replacing surd/nthroot by fractional powers", and the result is not always correct.

I get strange results when I try to input this expression. Is there a way to get the same result as on the image, without "temporary replacing surd/nthroot by fractional powers"?
03-22-2018, 08:41 PM
Post: #2
 Didier Lachieze Senior Member Posts: 1,169 Joined: Dec 2013
RE: formula with radicals
With the correct link to the picture:
03-22-2018, 09:12 PM
Post: #3
 Darno Junior Member Posts: 11 Joined: Mar 2018
RE: formula with radicals
(03-22-2018 08:41 PM)Didier Lachieze Wrote:  With the correct link to the picture:

Thank you. What did I do wrong then? I copied the link from the site and pasted it.
03-23-2018, 01:52 AM
Post: #4
 Joe Horn Senior Member Posts: 1,611 Joined: Dec 2013
RE: formula with radicals
Go into CAS Settings, and change Simplify to Maximum, and put a checkmark in the "Use i" box. Then one keystroke (Enter) will give you the result shown on the chalkboard. If two keystrokes is ok, leave the Simplify setting at its default (Minimum) and tap the "simplify" softkey after you get the initial result.

<0|ɸ|0>
-Joe-
03-23-2018, 02:06 AM
Post: #5
 Darno Junior Member Posts: 11 Joined: Mar 2018
RE: formula with radicals
(03-23-2018 01:52 AM)Joe Horn Wrote:  Go into CAS Settings, and change Simplify to Maximum, and put a checkmark in the "Use i" box. Then one keystroke (Enter) will give you the result shown on the chalkboard. If two keystrokes is ok, leave the Simplify setting at its default (Minimum) and tap the "simplify" softkey after you get the initial result.

Thank you! It was already set to Maximum, but changing it to Minimum (!) and checking Use i" did the trick.
Only, I got the (correct) result not in radicals but integers:
7*2^1/3*x^1/3*x

Any way to change that to the correct format?

Thanks again!
03-23-2018, 02:17 AM
Post: #6
 Joe Horn Senior Member Posts: 1,611 Joined: Dec 2013
RE: formula with radicals
(03-23-2018 02:06 AM)Darno Wrote:  I got the (correct) result not in radicals but integers:
7*2^1/3*x^1/3*x

Any way to change that to the correct format?

Hmmm... Anybody know of a way to change fractional powers to radical notation? I can't find it.

Suggestion: For now, just accept that they are two ways of writing the same thing, and toggle between them in your head, which thankfully is easy to do.

<0|ɸ|0>
-Joe-
03-23-2018, 02:54 AM
Post: #7
 Darno Junior Member Posts: 11 Joined: Mar 2018
RE: formula with radicals
(03-23-2018 02:17 AM)Joe Horn Wrote:
(03-23-2018 02:06 AM)Darno Wrote:  I got the (correct) result not in radicals but integers:
7*2^1/3*x^1/3*x

Any way to change that to the correct format?

Hmmm... Anybody know of a way to change fractional powers to radical notation? I can't find it.

Suggestion: For now, just accept that they are two ways of writing the same thing, and toggle between them in your head, which thankfully is easy to do.

No problem. I am just disappointed in the Cas hype.

Anyway, thanks again.
03-23-2018, 09:18 AM
Post: #8
 DrD Senior Member Posts: 1,124 Joined: Feb 2014
RE: formula with radicals
(03-23-2018 02:17 AM)Joe Horn Wrote:
(03-23-2018 02:06 AM)Darno Wrote:  I got the (correct) result not in radicals but integers:
7*2^1/3*x^1/3*x

Any way to change that to the correct format?

Hmmm... Anybody know of a way to change fractional powers to radical notation? I can't find it.

I tried to chase that down, too, with no luck. Cyrille posted a response on this topic:

-Dale-
03-23-2018, 01:25 PM
Post: #9
 Darno Junior Member Posts: 11 Joined: Mar 2018
RE: formula with radicals
(03-23-2018 09:18 AM)DrD Wrote:
(03-23-2018 02:17 AM)Joe Horn Wrote:  Hmmm... Anybody know of a way to change fractional powers to radical notation? I can't find it.

I tried to chase that down, too, with no luck. Cyrille posted a response on this topic:

-Dale-

Thanks Dale for the link. Apparently it is not that easy if even senior members don't know how to get it done.
I must say I find it strange because it looks like a straightforward conversion of symbols with no new computations involved.
03-23-2018, 01:44 PM (This post was last modified: 03-23-2018 02:17 PM by toshk.)
Post: #10
 toshk Member Posts: 189 Joined: Feb 2015
RE: formula with radicals
There exist the function; sqrfree()
If you can massage your surds in squares 2x it might help you.
Btw classpad gives the above example answered in indices form up the 4th line: impressive for this Dino
03-23-2018, 02:33 PM (This post was last modified: 03-23-2018 02:36 PM by Darno.)
Post: #11
 Darno Junior Member Posts: 11 Joined: Mar 2018
RE: formula with radicals
(03-23-2018 01:44 PM)toshk Wrote:  There exist the function; sqrfree()
If you can massage your surds in squares 2x it might help you.
Btw classpad gives the above example answered in indices form up the 4th line: impressive for this Dino

Thank you for the tip.
I wonder why HP has not implemented it yet. The Prime has been out for 5 years or more. It should not take programming skills to get results promised by Cas: textbook symbols.
But I do not want to turn this thread in HP-bashing or trolling. So, let us leave it at that.

edit: do you mean the casio classpad ii fx-cp400?
03-23-2018, 03:03 PM
Post: #12
 toshk Member Posts: 189 Joined: Feb 2015
RE: formula with radicals
Well Prime is a BEAST.... littered with impressive functions!!
What you are looking for can be found on Prime too;
The function is
Mult_conjugate() and it returns same as Classpad.
03-23-2018, 03:20 PM
Post: #13
 Darno Junior Member Posts: 11 Joined: Mar 2018
RE: formula with radicals
(03-23-2018 03:03 PM)toshk Wrote:  Yes classpad 400!!
Well Prime is a BEAST.... littered with impressive functions!!
What you are looking for can be found on Prime too;
The function is
Mult_conjugate() and it returns same as Classpad.

I like the Prime too. I hope my criticism will be understood as a constructive one.
I think that the result should be given directly in the textbook format, like that is mostly the case, with a toggle to choose different formats, without having first to look for a special function or write a dedicated program.
Let us hope HP will find the time for that since it is obviously doable.
03-26-2018, 11:09 AM
Post: #14
 parisse Senior Member Posts: 1,093 Joined: Dec 2013
RE: formula with radicals
The CAS main task is to compute, for this reason evaluation does not necessarily return an answer that follow the conventions of one specific country. Fractional powers of integers will always evaluate to something with ^. You can convert symbolic expressions to NTHROOT with the following little function:
Code:
f(ex):=subst(ex,'^',(a,b)->surd(a,inv(b)))
Then f(x^(1/3)) will return an NTHROOT.
03-26-2018, 02:02 PM
Post: #15
 DrD Senior Member Posts: 1,124 Joined: Feb 2014
RE: formula with radicals
Parisse,

A syntax error at the '^' point, with CAS mode on the virtual calculator?

-Dale-
03-26-2018, 02:14 PM
Post: #16
 parisse Senior Member Posts: 1,093 Joined: Dec 2013
RE: formula with radicals
Copy/paste does not work in textbook mode, only in algebraic mode or inside a program.
03-26-2018, 03:36 PM
Post: #17
 DrD Senior Member Posts: 1,124 Joined: Feb 2014
RE: formula with radicals
Great. Thank you!

-Dale-
03-27-2018, 03:29 AM (This post was last modified: 03-27-2018 03:30 AM by Eddie W. Shore.)
Post: #18
 Eddie W. Shore Senior Member Posts: 1,098 Joined: Dec 2013
RE: formula with radicals
Here are the results when I use sqrfree, collect, and expand having Simplification to both Minimum and Maximum:

2018-03-26 simplification example by Edward Shore, on Flickr

To add images, the at image has to be connected to an online URL. This can be from a blog or a photo posting site, such as Flickr.
03-28-2018, 06:54 PM
Post: #19
 Darno Junior Member Posts: 11 Joined: Mar 2018
RE: formula with radicals
(03-27-2018 03:29 AM)Eddie W. Shore Wrote:  Here are the results when I use sqrfree, collect, and expand having Simplification to both Minimum and Maximum:

2018-03-26 simplification example by Edward Shore, on Flickr

To add images, the at image has to be connected to an online URL. This can be from a blog or a photo posting site, such as Flickr.

In other words, nothing helps?
Thanks, Eddie, great job! It certainly clarifies the object of discussion.
03-29-2018, 02:10 PM (This post was last modified: 03-29-2018 02:12 PM by Darno.)
Post: #20
 Darno Junior Member Posts: 11 Joined: Mar 2018
RE: formula with radicals
of the three main cas calculators, Prime, Nspire and ClasspadII, only the Prime factors the original x^4 (in the chalkboard formula) into x(x^1/3). The other two apparently have a problem with that and simply use x^4/3, unfactored.
That is certainly an advantage of the Prime above the other two.
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