Programming TI-83plus? Help

Hacp

Lifer
Jun 8, 2005
13,923
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Hi all,
I am trying to program my Ti-83 plus to do things. So far, I have managed the simple stuff, like loops. I'm just confused about arrays. How do you make one on the Ti-83? Also, how do you define a function in the Ti-83 plus and pass variables? My motivations are simple. To program equations that are dependent on many variables into my calculator. For example, I might have a function G(T(R(H(x,y))) and I might have constraint equation G(x,y)-Z(x)=0 and I need to loop through x and y until the constraint is satisfied. At the same time, G might be defined but x would be non-linear and not defined so I need to use an iterative process to solve for x in order to calculate Z. How would I do that in the Ti-83?
 
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degibson

Golden Member
Mar 21, 2008
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Wow... this is a blast from the past for me. My answers are from 11-year stale memory on a TI-83.

FYI, TI-83's are a lot less full-featured than many languages to which you may be accustomed.

Hi all,
I am trying to program my Ti-83 plus to do things. So far, I have managed the simple stuff, like loops. I'm just confused about arrays. How do you make one on the Ti-83?
Use one of the available global 'list' variables.

Also, how do you define a function in the Ti-83 plus and pass variables?
Sorry -- there are no functions. There are no scoped arguments. You can define another program that assumes inputs in global variables and writes outputs into global variables, then call that program from another program to emulate a function call.

My motivations are simple. To program equations that are dependent on many variables into my calculator. For example, I might have a function G(T(R(H(x,y))) and I might have constraint equation G(x,y)-Z(x)=0 and I need to loop through x and y until the constraint is satisfied.

Maybe possible on a TI-83, but this will take a long time for something nontrivial. IIRC, TI-89s (or 92s?) were capable of bivariate analysis, e.g., finding the zeros of z=f(x,y), via their builtins, but not the TI-83.

At the same time, G might be defined but x would be non-linear and not defined so I need to use an iterative process to solve for x in order to calculate Z. How would I do that in the Ti-83?
Is x not an independent variable here? I'm not clear on what you mean by 'not linear'. If x is a non-linear function of some other variable, you'll want to use that other variable as input parameter and further nest your G(T(R(H(x(whatever),y)))).
 

Hacp

Lifer
Jun 8, 2005
13,923
2
81
Wow... this is a blast from the past for me. My answers are from 11-year stale memory on a TI-83.

FYI, TI-83's are a lot less full-featured than many languages to which you may be accustomed.


Use one of the available global 'list' variables.


Sorry -- there are no functions. There are no scoped arguments. You can define another program that assumes inputs in global variables and writes outputs into global variables, then call that program from another program to emulate a function call.



Maybe possible on a TI-83, but this will take a long time for something nontrivial. IIRC, TI-89s (or 92s?) were capable of bivariate analysis, e.g., finding the zeros of z=f(x,y), via their builtins, but not the TI-83.


Is x not an independent variable here? I'm not clear on what you mean by 'not linear'. If x is a non-linear function of some other variable, you'll want to use that other variable as input parameter and further nest your G(T(R(H(x(whatever),y)))).

You know G, but you don't know x and you're asked to calculate x. So an equation like
h=x*123*+x^1/3+ln(x)*tan(x)*y
g=(ln(h^2)*120/.003)^.04
and you're given G and y is assumed to be 1, so find x such that G(x,y)-Z(x)=0 where Z(x)=(15^x)*120x^2.

I just made these equations from my ass but that's the kind of equations I'm looking to solve.
 

Gamingphreek

Lifer
Mar 31, 2003
11,679
0
81
You know G, but you don't know x and you're asked to calculate x. So an equation like
h=x*123*+x^1/3+ln(x)*tan(x)*y
g=(ln(h^2)*120/.003)^.04
and you're given G and y is assumed to be 1, so find x such that G(x,y)-Z(x)=0 where Z(x)=(15^x)*120x^2.

I just made these equations from my ass but that's the kind of equations I'm looking to solve.

Sounds like you are trying to Symbolically Solve Equations on the TI83... something which isn't possible unless you have an 84 or 89.

-GP
 

Gamingphreek

Lifer
Mar 31, 2003
11,679
0
81
Not symbolically. Numerically.

Yes but the TI83 doesn't recognize variables symbolically. It assumes instantiation (ie: Assumes that a number is stored at variable 'X'), thus the reason why the 84 and 89 are so valuable. They are able to solve equations in that manner while leaving the variables as a symbolic representation.

My terminology may be throwing off what I am trying to say ;)

-GP
 

Hacp

Lifer
Jun 8, 2005
13,923
2
81
Yes but the TI83 doesn't recognize variables symbolically. It assumes instantiation (ie: Assumes that a number is stored at variable 'X'), thus the reason why the 84 and 89 are so valuable. They are able to solve equations in that manner while leaving the variables as a symbolic representation.

My terminology may be throwing off what I am trying to say ;)

-GP

I'm not talking about symbolic variables. For example, you are given G=25. You need to iterate to find x and see if Z(x)=25.
 

Hacp

Lifer
Jun 8, 2005
13,923
2
81
I guess I'll add if/while loops in there. Is there any way to define more than 26 variables? There are only 26 letters in the alphabet and the calc can't recognize two letter variables like XS or AB or AC. Thanks.
 

degibson

Golden Member
Mar 21, 2008
1,389
0
0
There's a much easier way to do this. Use the calculator's graphing functions. Define your Y-variable on the command prompt, then plug in your formula for G(x,y), except as Y=G(x,y)-G0, where G0 is the known value for G. Then ask the TI-83 to find the y-intercept.

I.e., continuing with the example, and supposing your target G0 value is 55:
Y <- 1
[enter graphing mode with y= button]
Y1 = x*123*+x^1/3+ln(x)*tan(x)*y
Y2 = (ln(Y2^2)*120/.003)^.04
Y3 = (15^x)*120x^2
Y4 = Y2 - Y3 - 55
[graph Y4, use math menu to find y-intercept]
 
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