nSolve on a CX versus a CX CAS, how to guess a negative value?

[Hartman, Bruce]

Ok, I was teaching exponentials in my Precalc class...  I usually use the CAS emulator at all times while teaching, as I teach Calculus as well.  So we were solving this equation.  I used Algebra --> nSolve on my CAS, assuming it would work like nSolve on the regular CX.  However....

  Same result with an actual CX Handheld (non II)

   Same result with an actual CX CAS Handheld (non II)

Why if I use nSolve on both, I do not get an answer on the regular CX?

While we are here.... I had an issue with nSolve in my Calculus class too.

Isn't the syntax for nSolve( equation, variable, guess) ???  We were doing this problem...  We were working on an interval of [0, pi/2], but I wanted to show them how to "Guess" as this value  will repeat each 2pi.  It worked to the right...., but to the left it would NOT pick up the negative values of "C" that had a slope of 4/pi.  Also was training to use nSolve to get 1 solution as a CAS Solve command gives multiple/all solutions and can be messy at times.  

Thanks,

Bruce

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[epi van winsen]

The syntax is:

nSolve( equation, variable[=guess],lower[,upper])) between [ ] is optional.

The guess value has to have an equal-sign

More syntax is possible. You find it in the library when you go to the nSolve() command.

Best regards,

Epi van Winsen

[Peggy Frisbie]

I would recommend the use of a restricted domain instead of the guess. You do that with the "when" bar from the inequality menu, like this:

It works with solve on a CAS to give all of the solutions in the interval instead of the annoying n1 notation. (I did use Ctrl-Enter to get decimal results for the solve() command.) I think this has the advantage of being more like we think of it mathematically.

[Hartman, Bruce]

Still shouldn't be this hard.  Shouldn't it start looking for solutions where I "guess"?   I tried the restricted domain of x>-1.5 , but it STILL only gave me the positive answer only!

I finally had to say 0>x>-1.5, only look in the negative part of my interval for the negative answer to ever show up!  I shouldn't have to do that.  My expectation is it starts at the left of my interval, and give me the 1st solution it finds L to R.  Then, I realize with nSolve I need to double check for possible other solutions.  The only way to get that 1st zero in the negative side of my interval, I had to do the negative side of my interval separate from the positive side of my interval.  I also double checked entering the interval the other was around, and it didn't matter.  At this point, I might as well just tell my students to graph it to see the zeros...

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[John Hanna]

It probably starts in the ‘middle’ of the interval.

 

From: tins...@googlegroups.com <tins...@googlegroups.com> On Behalf Of Hartman, Bruce
Sent: Thursday, January 27, 2022 11:27 AM
To: tinspire <tins...@googlegroups.com>
Subject: Re: [tinspire] Re: nSolve on a CX versus a CX CAS, how to guess a negative value?

 

 

Still shouldn't be this hard.  Shouldn't it start looking for solutions where I "guess"?   I tried the restricted domain of x>-1.5 , but it STILL only gave me the positive answer only!

 

I finally had to say 0>x>-1.5, only look in the negative part of my interval for the negative answer to ever show up!  I shouldn't have to do that.  My expectation is it starts at the left of my interval, and give me the 1st solution it finds L to R.  Then, I realize with nSolve I need to double check for possible other solutions.  The only way to get that 1st zero in the negative side of my interval, I had to do the negative side of my interval separate from the positive side of my interval.  I also double checked entering the interval the other was around, and it didn't matter.  At this point, I might as well just tell my students to graph it to see the zeros...

 

 

 

 

On Wed, Jan 12, 2022 at 12:35 PM Peggy Frisbie <peggyf...@gmail.com> wrote:

I would recommend the use of a restricted domain instead of the guess. You do that with the "when" bar from the inequality menu, like this:

 

It works with solve on a CAS to give all of the solutions in the interval instead of the annoying n1 notation. (I did use Ctrl-Enter to get decimal results for the solve() command.) I think this has the advantage of being more like we think of it mathematically.

On Tuesday, January 11, 2022 at 9:22:15 AM UTC-5 Bruce Hartman wrote:

Ok, I was teaching exponentials in my Precalc class...  I usually use the CAS emulator at all times while teaching, as I teach Calculus as well.  So we were solving this equation.  I used Algebra --> nSolve on my CAS, assuming it would work like nSolve on the regular CX.  However....

 

  Same result with an actual CX Handheld (non II)

 

   Same result with an actual CX CAS Handheld (non II)

 

Why if I use nSolve on both, I do not get an answer on the regular CX?

 

While we are here.... I had an issue with nSolve in my Calculus class too.

Isn't the syntax for nSolve( equation, variable, guess) ???  We were doing this problem...  We were working on an interval of [0, pi/2], but I wanted to show them how to "Guess" as this value  will repeat each 2pi.  It worked to the right...., but to the left it would NOT pick up the negative values of "C" that had a slope of 4/pi.  Also was training to use nSolve to get 1 solution as a CAS Solve command gives multiple/all solutions and can be messy at times.  

 

 

 

Thanks,

Bruce

 

 

To view this discussion on the web visit https://groups.google.com/d/msgid/tinspire/CAHuFaWgxhdAgFP-sRgfNKDgjEyAzdY%3DwBgabVK0o_8bevU-szw%40mail.gmail.com.

[John Hanna]

… and the window matters when you do it from the graph.

 

From: tins...@googlegroups.com <tins...@googlegroups.com> On Behalf Of Hartman, Bruce
Sent: Thursday, January 27, 2022 11:27 AM
To: tinspire <tins...@googlegroups.com>
Subject: Re: [tinspire] Re: nSolve on a CX versus a CX CAS, how to guess a negative value?

 

 

Still shouldn't be this hard.  Shouldn't it start looking for solutions where I "guess"?   I tried the restricted domain of x>-1.5 , but it STILL only gave me the positive answer only!

 

I finally had to say 0>x>-1.5, only look in the negative part of my interval for the negative answer to ever show up!  I shouldn't have to do that.  My expectation is it starts at the left of my interval, and give me the 1st solution it finds L to R.  Then, I realize with nSolve I need to double check for possible other solutions.  The only way to get that 1st zero in the negative side of my interval, I had to do the negative side of my interval separate from the positive side of my interval.  I also double checked entering the interval the other was around, and it didn't matter.  At this point, I might as well just tell my students to graph it to see the zeros...

 

 

 

 

On Wed, Jan 12, 2022 at 12:35 PM Peggy Frisbie <peggyf...@gmail.com> wrote:

I would recommend the use of a restricted domain instead of the guess. You do that with the "when" bar from the inequality menu, like this:

 

It works with solve on a CAS to give all of the solutions in the interval instead of the annoying n1 notation. (I did use Ctrl-Enter to get decimal results for the solve() command.) I think this has the advantage of being more like we think of it mathematically.

On Tuesday, January 11, 2022 at 9:22:15 AM UTC-5 Bruce Hartman wrote:

Ok, I was teaching exponentials in my Precalc class...  I usually use the CAS emulator at all times while teaching, as I teach Calculus as well.  So we were solving this equation.  I used Algebra --> nSolve on my CAS, assuming it would work like nSolve on the regular CX.  However....

 

  Same result with an actual CX Handheld (non II)

 

   Same result with an actual CX CAS Handheld (non II)

 

Why if I use nSolve on both, I do not get an answer on the regular CX?

 

While we are here.... I had an issue with nSolve in my Calculus class too.

Isn't the syntax for nSolve( equation, variable, guess) ???  We were doing this problem...  We were working on an interval of [0, pi/2], but I wanted to show them how to "Guess" as this value  will repeat each 2pi.  It worked to the right...., but to the left it would NOT pick up the negative values of "C" that had a slope of 4/pi.  Also was training to use nSolve to get 1 solution as a CAS Solve command gives multiple/all solutions and can be messy at times.  

 

 

 

Thanks,

Bruce

 

 

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[John Hanna]

Strange, but I sent THIS post a few seconds before the one about the window.

To view this discussion on the web visit https://groups.google.com/d/msgid/tinspire/001e01d813a2%241e725a30%245b570e90%24%40optonline.net.

[Ryan Tebble]

I just got this... can someone please advise, what's wrong/what we need to fix. I tried restricting domains... still says no solutions. Both CAS and NON CAS CXII

To view this discussion on the web visit https://groups.google.com/d/msgid/tinspire/003501d813b0%24c0c49470%24424dbd50%24%40optonline.net.

[John Hanna]

What does the graph look like?

 

From: tins...@googlegroups.com <tins...@googlegroups.com> On Behalf Of Ryan Tebble
Sent: Thursday, February 10, 2022 12:53 AM
To: tins...@googlegroups.com
Subject: Re: [tinspire] Re: nSolve on a CX versus a CX CAS, how to guess a negative value?

 

I just got this... can someone please advise, what's wrong/what we need to fix. I tried restricting domains... still says no solutions. Both CAS and NON CAS CXII

To view this discussion on the web visit https://groups.google.com/d/msgid/tinspire/CAAc5kWWvv4akPY1NYPzZ816TQF1pC6gJv9241twgN2%3D960K-ZA%40mail.gmail.com.

[Ryan Tebble]

To view this discussion on the web visit https://groups.google.com/d/msgid/tinspire/011501d81e67%2459cd6f50%240d684df0%24%40optonline.net.

[John Hanna]

Then use [menu] Analyze > Intersection (there are 2 intersections).

 

From: tins...@googlegroups.com <tins...@googlegroups.com> On Behalf Of Ryan Tebble
Sent: Thursday, February 10, 2022 6:36 AM
To: tins...@googlegroups.com
Subject: Re: [tinspire] Re: nSolve on a CX versus a CX CAS, how to guess a negative value?

 

To view this discussion on the web visit https://groups.google.com/d/msgid/tinspire/CAAc5kWW_RXY9MLxtURPDq4R5mtSnLKSvWwNfvs3c37aip5ikEQ%40mail.gmail.com.

[Hartman, Bruce]

I think that our questions are to understand WHY we are getting "no solutions" using the nSolve or Solve commands.  There are times where I just need the answer, and do not want to take the time to graph it,  adjust windows, and then run the Intersection tool.  We should get results from nSolve if there is a real solution without all the hassle.  Though, with all the issues I've had this year, I am about to just have my AP Calc students graph everything... :-(

Bruce

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[Ryan Tebble]

Precisely... there seems to be an error with nsolve/solve on the CXII. Finding the solution by other methods is irrelvant. Students wasting time in an exam, when nsolve should work but doesn't, can actually do quite a lot of harm. 

Has TI corrected this issue in an update? As surely its been reported to them. 

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