Trig values when using degrees in radian mode

[Hartman, Bruce]

A colleague of mine brought a question to me today.  She has students keep their calculators in Radian mode, and has them "override" with the degree symbol when necessary instead of switching back and forth in the Document Settings.  Below is a screen shot.  The top half of the screen, the calculator was in Degree mode, and bottom half in Radian mode.  Why in radian mode does it not return undef and 0 when you override with degrees?  

Thanks,

Bruce

 

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[roryd...@gmail.com]

The problem seems to be that the TI-Nspire calculates either pi or 180 degrees differently in the radians and the degrees mode. I cannot tell the exact difference right now.

Here is the same simple calculation done twice, first in Degrees mode, then in Radians mode.

[Ray Cross]

Hi all,

Seems ok in Navigator OS 4.2 software.

I thought it may be dependent on settings due to irrational pi; but Float and Float 6 didn't return any inconsistencies

when the screens below were replicated.

Also no problem in Scratchpad.

Is it a HH issue?

Cheers,

Ray

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[Hartman, Bruce]

Now that's weird because I did my original screen shots using Navigator 4.2 software.  I even changed to Float 12 thinking it was something in the decimals of pi.  Ray, did you do it on the regular CX software?  I didn't try it on the CAS version.

[Jody Crothers]

Hi all
I am trying to convert a string to a binary output
the following works converting a string to ascii but i cant get the ▶Base2 command to work, any ideas

Define code(input)=
Func
:Local list,k,instr,g
:list:={}
:If getType(input)≠"STR" Then
:input:=string(input)
:EndIf
:instr:=input
:If dim(input)>1 Then
:For k,1,dim(input)
:© returns ascii value then  I want to change to binary▶Base2
:list[k]:=ord(left(instr,1)) Putting it here gives me a syntax error
:instr:=shift(instr,1)
:EndFor
:Return list
:Else
:©returns ascii value
:Return ord(input)
:EndIf
:EndFunc

cheers
Jody

[Jody Crothers]

c▶Base2 works with list in calculator page but not in basic

Here is an easier program

Define encode(a)=
Prgm
:str21st(streng):=seq(mid(streng,x,1),x,1,dim(streng))
:b:=str21st(a)
:Disp b
:c:=ord(b)
:Disp c
:d:=c▶Base2 THIS bit doesnt work give me a syntax error AHHHH but it works on calculator page
:EndPrgm

[Ray Cross]

G'day Bruce,

All done on Navigator CX CAS OS 4.2.
Didn't  generate any inconsistencies at all.
Somewhat of a mystery!

Cheers,

Ray

[Sean Bird]

Is Bruce using the numeric Nspire and Ray using CAS?

1E-13 would be close enough to zero in a numeric world, but in the 'exact' world of CAS sometimes it would do better than 1E-13...maybe.

Sean Bird
AP Calculus & Physics,
NHS Adviser & Rocket Team Supervisor
Math & Science Technology Coordinator
Covenant Christian High School
7525 West 21st Street
Indianapolis, IN 46214
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Website: http://covenantchristian.org/bird
work Email: sean...@covenantchristian.org
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Psalm 111:2 “Great are the works of the LORD, studied by all who delight in them.”

[Hartman, Bruce]

Thanks for the replies guys...

Ray - I was using the numerical CX Navigator, so that lies the problem I face.  For the students taking the Regents in NY can not use the CAS.  I agree with Sean that -1E-13 I think most students can see is nearly zero, BUT where they should see UNDEF they are getting a number -1E13 and have a harder time see that as undefined.  I am not surprised that the CAS version is doing it correctly as it is not performing a numerical calculation... CAS can work in the exacts of pi and irrational numbers algebraically.

Is there a setting on the numerical CX HH/Navigator that will raise the accuracy so it indeed will return 0 and undef when over riding with degree symbol in radian mode?  I guess that is the question I am wondering about.

Thanks again all...

Bruce

[Csaba Tizedes]

The real reason is that, the PI is a symbolic constant AND PI is irrational.
Therefore no ANY number which is equal with PI if you want to make calculation or want to store in a variable for 14-15 digits.

Your example perfectly shows this, but you can make more thorough examination this feature, if you make all the possible permutations that will clearly shows what happen and why you get 1.E-13 as result - check the attached picture or check this pdf.

You get 1.E-13, because the difference between 9.8E-12 and 9.7E-12 is 1.E-13, but must to understand the REAL reason is that, the PI is a symbolic constant AND PI is irrational.

Attached picture here

Csaba