Index: (There are forty more FAQs on page 1.  Click page 2 under TI FAQs in the navigation panel to go there.)

(41) How do I make the screen brighter on a TI-83Plus?
(42)  How can I find the area under a curve on a TI-83 Plus?
(43)  Our professor wants us to show our work on a Simplex problem.  Can I use a TI-83Plus to do the row operations by hand?
(44)  How do I do a scatter plot on a TI-83 Plus?
(45)  How do I do an x-y line chart on a TI-83 Plus?
(46)  How do I do a histogram on a TI-83 Plus?
(47)  When I do fPart of a number like (4/3)3, I get 1. Why is that?
(48)  Is there a way to keep from accidentally changing or deleting programs?
(49)  During the summer when I'm not in school, should I remove the AAA batteries?
(50)  Why will I loose my programs if I remove all batteries.
(51)  What's the purpose of garbage collect.
(52)  Should I run garbage collect periodically?
(53)  You say that the TI-83 Plus and the TI-84 Plus use the same CPU.  I know enough about electronics to say that if they have
          the same CPU, they run at the same speed.
(54)  Will your program FACTOR solve equations like 4sec²x + cotx -7?
(55)  What is the main difference between the TI-83 Plus and the TI-84 and how do the prices compare?
(56)  I get an error message doing IRR.  Why?
(57)  How do I write a program for my TI-84 on my computer?
(58)  How do I transfer a program from my computer to my TI-84 calculator?
(59)  How do I transfer a program from my calculator to my computer?
(60)  My quartile values don't agree with Minitab.  Is there something wrong with my calculator?
 

Revised: 2/11/10

Answers:

(41) How do I make the screen brighter on a TI-83Plus?
Press 2nd; then press the up arrow.  If the screen is not set to maximum, it should get brighter.  If you get it too bright the down arrow will decrease the brightness.
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(42)  How can I find the area under a curve on a TI-83Plus?
1)  Press Y=, and enter your function in the usual manner in the Y1=  position.
2)  Press 2nd; then CALC (2nd function of TRACE).
3)  The calculator will go to the graphing screen and ask for the lower limit.  There are two ways to enter the limit:  a)  Just punch in the number and press ENTER, and b)  Move the cursor to where you want it and press ENTER. 
4)  The calculator will now ask for the upper limit.  Enter that in either of the above ways. The area will be displayed after you enter the upper limit.
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(43)  Our professor wants us to show our work on a Simplex problem.  Can I use a TI-83Plus to do the row operations by hand?
Well, yes, all of the gory details of row operations are in FAQ 21 on the first page.  So, I'll just give you a summary here. 
First of all, I suggest that you enter your first tableau in matrix [B], and then use STO to transfer it to matrix [A]. That way you can work on matrix [A], and if you make a mistake you won't need to re-enter the original matrix.  Just transfer it from [B] to [A] again.  (If you don't know how to enter the first tableau see FAQ 19 on the first page.)  So, you'll need several row operations described as follows:
   1)  Multiply one row by a number and add it to another number.  Say, multiply row 2 by -2 and add that to row 2.
      a)  From the home screen, press 2nd, MATRIX; scroll over to MATH; scroll down to item F, and press  ENTER.  You should now have *row+( on your home screen.
      b)  Now you want to enter the multiplier, letter of the matrix, row number multiplied by, row number to replace in that order.  Do this:  Enter -2, press the comma button, press 2nd, MATRIX, ENTER.  You should now have *row+(-2, [A] on your screen.  DO NOT enter [A] with the brackets and the letter A.
      c)  Now press the comma button, enter 1;  press the comma button and enter 2.  You should now have *row+(-2,[A],1,2 on your screen.
      d)  Press STO, 2nd, MATRIX, ENTER.
      e)  You should now have *row+(-2,[A], 1,2►[A] on your screen.  DO NOT enter [A] with the brackets and the letter A.  (Note carefully that if you don't add the STO, [A], then matrix A will not be changed in your calculator.   Also notice that you can either close the parentheses after the last row number or leave them open.)
   Note that if you have another operation of this type you can press 2nd, ENTER, and then edit the entry that appears for the proper multiplier and row numbers.
2)  Multiply a row by a number.
      Now, multiply row 2 by -1/5 as follows:  *row(-1/5,[A],2►[A].
3)  Add two rows say 1 and 2.
    If you want to add two rows; then the syntax is this: row+(matrix letter, row to be added, row to be replaced)►[A]
4)  Swap two rows.
     To swap rows, use this syntax:  rowSwap(matrix letter, first row, second row►[A].
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(44)  How do I do a scatter plot on a TI-83 Plus?
First you need to get your data into lists. 
1)  First go to the graphing screen by pressing the Y= button and deselecting any  functions so that they won't be entered on your graph.
 2)  Press [STAT], [ENTER]
3)  Then enter the data-point numbers ( the x-values)  in L1 and the corresponding values (y-values)  in L2.  (If your data is not in order you can sort in order by pressing [STAT], select 2, SortA( or SortD( for descending order.  SortA( , or SortD( will be posted to the home screen.  Press [2nd], L₁, 2nd, L2, [ENTER].  Be careful!  If your data in L₂ is not in ascending order when correlated to L_1, then your data in L₁ and L₂ will not be correlated correctly.)
4)  Press [2nd], [QUIT]
5)  Press [2nd], [STAT PLOT] and press [ENTER] to turn Plot 1 on.
6)  Cursor to the scatter diagram on Type and press [ENTER] to highlight the scatter diagram.
7)  Enter L₁ in the Xlist, and L₂ in the Ylist (do this by pressing 2nd and the appropriate list button);  then select the type marker you prefer.  (I like the + symbol. ).
8)  Press [GRAPH] and the scatter plot will appear on the screen.
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(45)  How do I do an x-y line chart on a TI-83 Plus?
Do that the same as the scatter plot in FAQ 44 above except that when you select the type, choose the line symbol rather that the scatter symbol.
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(46)  How do I do a histogram on a TI-83 Plus?
This procedure will do a simple histogram in which the calculator selects the class width.
First you need to get your data into lists. 
1)  First go to the graphing screen by pressing the Y= button and deselecting any  functions so that they won't be entered on your graph.
 2)  Press [STAT], [ENTER]
3)  Then enter the data-point numbers ( the x-values)  in L₁.
4)  Press [2nd], [QUIT]
5)  Press [2nd], [STAT PLOT] and press [ENTER] to turn Plot 1 on.
6)  On the next screen highlight ON to turn the plot on, highlight the histogram symbol and enter the list number for the data in Xlist, (for example L₁).  Leave Freq at the default of 1 unless you have "tabled" data, in which case you will not use this method.
7) Press ZOOM; then 0 (ZoomFit) and your histogram will be displayed.
8)  You can use [TRACE] to display the value and boundaries of a particular bar on the histogram.
If you want to set your own classes, go to FAQ 32 on page 1. You can get there by going to the navigation bar to your left and clicking on More Detailed Page 1.
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(47)  How do I do a regression and graph the scatter plot and the regression equation on the same axis on a TI-83 Plus?
First you need to get your data into lists.
Press [STAT], [ENTER]
Then enter the data-point numbers (the x-values) in L1 and the corresponding values (y-values) in L2.
Press [2nd], [QUIT]

Now, to do the scatter plot.
Now, you want to put the scatter plot on the screen with the graph. So do this:
1) Press [2nd], [STAT PLOT] and press [ENTER] to turn Plot 1 on.
2) Cursor to the scatter diagram on Type (the first icon) and press [ENTER] to highlight the scatter diagram.
3) Enter L1 in the Xlist, and L2 in the Ylist; the select the type marker you prefer. (I like a + ).
4) Press [GRAPH] the scatter plot will appear on the screen.
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(47)  When I do fPart of a number like (4/3)3, I get 1. Why is that?
Bottom line:  I don't know.  But...I do have a guess that goes something like this:  When the calculator calculates 1/3 it comes up with .3333333333.  Now, if we multiply that 3, by hand, we'll get .9999999999.  But if you do it on the calc, you'll get 1.  So, my guess is that the fPart decides that .9999999999 is a fractional part, but the display prints it as 1.  If you have some free time, you could check this out and see if it holds water. 
The practical implications of this quirk are that if you're multiplying a proper fraction by a whole number, e.g., (6/5)5, the fPart gives zero as expected.  But when you do an improper fraction such as the one you gave, you may get 1, 0, or a number like 1E-12 depending on your improper fraction.
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(48)  Is there a way to keep from accidentally changing or deleting programs?
Yes, you can archive the program; then un-archive it when you want to make deliberate changes.  Here's how to archive a program.
  a)  Press 2nd, MEM, 2.   (Pressing 2 selects 2:Mem Mgmt/Del...)
  b)  Press 7 (for Prgm), ENTER. 
  c)  Select the program you want to archive and press ENTER.  An asterisk will appear opposite the   
       program name indicating that it is archived.  With that, the program will be protected from being  
       deleted even when you upgrade the operating system.
When you want to un-archive the program and make some changes, do the following:
  a)  Press 2nd, MEM, 2.   (Pressing 2 selects 2:Mem Mgmt/Del...)
  b)  Press 6 (to select Unarchive).
  c)  Press PRGM, select the archived program you want to un-archive and press ENTER
  d)  Press ENTER again and the program will be un-archived and available for editing.
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(49)  During the summer when I'm not in school, should I remove the AAA batteries?
 No, leave them in.  When you remove the AAA batteries, the power for the RAM is supplied by the small circular battery (CR1616 or CR1620.)  If you leave the AAA batteries out too long, the circular battery will be discharged and you will lose any programs that you have in RAM..
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(50)  Why will I loose my programs if I remove all batteries.
 Well, I'm not exactly sure why you'd want to remove all of the batteries, but if you do, you'll lose anything that is stored in RAM.  Programs and applications that have been stored in flash ROM, archived programs, will not be lost.   But any un-archived programs will be lost since they are stored in volatile memory.  It's just like when you turn off your computer, you lose anything that hasn't been stored on a hard drive.
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(51)  What's the purpose of garbage collect.
  Well, without going into a lot of hand waving, you can think of it as being something like defrag on your computer.  Only applications can cross sector boundaries in your flash ROM.  So, if you have a lot of archived programs and variables, you'll eventually end up with a fragmented flash ROM.
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(52)  Should I run garbage collect periodically?
  For myself, I just let it go because it can take some considerable time to execute the garbage collect procedure.  I have a lot of programs that I've spend a lot of time on,  so to be ultra-safe, I back up my calculator before I'll let the calculator run garbage collect.  That can take quite a lot more time.  Anyway, when you try to archive a program with insufficient memory the calculator will ask you if you want  to garbage collect.  Of course, if you're a gamer or some other sort of guru and worry about all the nitty-gritty you can always run it.
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(53)  You say that the TI-83 Plus and the TI-84 Plus use the same CPU.  I know enough about electronics to say that if they have the same CPU, they run at the same speed.
    This is not really a calculator question, so I'm reluctant to deal with it, but here goes anyway.   I'm not sure if you're misinterpreting what I said or if you're confusing execution efficiency  with speed.  I'm pretty sure what I said was that both use the Z-80 CPU.  Now, I'm not an expert on CPU architecture, but I'm pretty sure that if one Z-80 takes, say, three clock cycles to do a particular operation, then another Z-80 will take the same number of clock cycles.  But if, for example,  the time for a clock cycle is cut to 1/3 its former time, the speed for that operation will be roughly  three times as fast. 
    Clock speed is highly dependent on technology and chip layout efficiency.  So, let's say that if the Z-80 of the TI-83 Plus is 3-micron technology  (admittedly pretty old stuff);  then if implemented in .35- or .25-micron technology,  for example, the clock speed could be much faster.  The smaller linewidths would result is shorter interconnect lines, and,  therefore, lower RC products; the  transistors will be faster  because of the shorter channel lengths; possibly some timing issues will be resolved due to a smaller chip, and, depending on the metallization thickness, possible even  a smaller RC product per unit length of interconnect.  That's enough.  Back to calculator questions.
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(54)  Will your program FACTOR solve equations like 4csc²x + cot x -7?
     No, you must first do some substitution. 
    csc² x= 1+cot² x.  After substitution you have:
   4(1+cot² x) + cot x - 7
           4cot² x + cot x -3
    This is fairly easy to factor by trial and error, but, if you want, you can let x = cot x with the resulting equation of
    4x² +x -3.  You can plug that into my program,  and it will give you the factors in terms of x.  You will need to
    replace each "x"  in the factors with cot x to get your factorization.
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(55)  What is the main difference between the TI-83 Plus and the TI-84 and how do the prices compare?
  The major differences between the TI-84 and the TI-83 Plus are that the TI-84 has more memory,   operates at a faster clock speed (about 2.5 times), and has more applications loaded.  Frankly, you might not notice the speed unless you're a gamer or running some long programs.   Although the TI-84 has more applications loaded,  you can download some of these free for the TI-83 Plus.  The TI-84 also has a clock, and the TI-83 Plus doesn’t if that’s important to you. 
  There are also some of new statistics functions is the TI-84 Plus Silver Edition. These are as follows:  Manual Fit under the STAT>Calc menu; X2 GOF-Test (X 2 means Chi-squared); and InvT under DISTR.  Frankly, I’m especially glad to see the InvT because I had to write a program for the TI-83 Plus to do that, but many students don’t have it.   There are also several Catalog items that may or may not have importance to you.   Here’s a list that I got somewhere, but I’ve never really check it out completely: χ²GOF-Test , checkTmr , ClockOff and ClockOn , dayOfWk , ExecLib, getDate, getDtFmt, getDtStr, getTime, getTmFmt, getTmStr, invT , isClockOn , LinRegTInt, Manual-Fit, OpenLib, setDate, setDtFmt, setTime, setTmFmt , startTmr , timeCnv.  Many of these are used in programs.  You should bear in mind that the TI-83 Plus possibly could not be produced much longer.
   If you're into games or you plan to use your calculator for many years, and if you're not on a tight budget, you might want to go with the TI-84.  Some schools that I know of, including ours, are migrating to the TI-84 Plus regular or Silver Edition, but you wouldn’t notice the difference with a TI-83 Plus, except, MAYBE, in a statistics class.  You can always use my program for InvT J.   It’s on my website in the statistics user guide.
    As to price, they vary all over the place, depending on where you live.  Check your Sunday newspaper supplement.  Be sure to include such places as Office Depot, Office Max, Staples, and Wal-Mart.
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(56)  I get an error message doing IRR.  Why?
       1)  If the first and last cash flows have opposite signs, you should get an IRR without problems.
       2)  If they do not have opposite signs, you may have problems according to the following:
           a)  If the cash flows all have negative signs, there will be no IRR.
           b)  If there are relatively small positive cash flows between negative first and last cash flows, you may
                either not obtain a solution or may get an invalid value. Of course, there's a vertical asymptote at
                -100%, but often you can run into problems considerably before you get there.In this situation,
                if you insist on solving this type problem you can graph it if the number of cash flows does not make
                the task too arduous.
                Very briefly, what you want to do is graph the following:
                Y1=C(0)+C(1)/(1+x)+C(2)/(1+x)²+C(1)/(1+x)³+...C(n)/(1+x)ⁿ
                 As a first try, set Xmax =2 and Xmin=-2.You can then find the value of the interest, X, using the
                 2ND, CALC, Zero, method discussed elsewhere in these documents. Let's take an example of
                 -500, 100, 200 , A, just to make the math simple.  As A becomes increasingly negative, the two
                 solutions move closer together so that at -63 the solutions about are -62% and -50.7%.  But if
                 A=-65 both of those solutions greater than -100% disappear and the calculator accurately gives
                 an error message.  Bottom line: If you plug in a negative number chosen at random, your calculator
                 is not malfunctioning if it gives an error message.
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(57)  How do I write a program for my TI-84 on my computer.
          Well, there may be more than one way to do it, but here's the way I do it.  First you must have the Graph Link software for
         the TI-83 Plus calculator.  That can be downloaded free from the TI Website. Once you get that installed, just click on the icon
         and the application will open.  It's pretty  straightforward from that point.  I suggest you save the file to a folder that you will
         use to transfer the program to your calculator.  I will deal with that transfer in the next FAQ.
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(58)  How do I copy a program from my computer to my TI-84 calculator?
          Here's the way I do it.
          a. Open TI-Connect and connect the calculator to the computer with the USB cable.
          b. Click on the TI-Device Explorer icon.
          c.  Open the folder where the program you want to copy to the calculator is stored.
          d. Drag that file to the TI-Device Explorer folder.
          e. Copying of the file will begin in a half minute or so.
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(59)  How do I copy a program from my TI-84 calculator to my computer?
          a. Open TI-Connect and connect the calculator to the computer with the USB cable.    
              Make sure the calculator is on.
         b. Click on the TI-Device Explorer icon.
         c. After the connection to the calculator is established and the list is displayed, expand Program by  
             clicking on the + mark beside “Program.”
        d. Highlight the program that you want to copy to the computer.
        e. Click on the File menu and select Copy to PC.
        f.  The folder "My Documents" will appear with the folders listed.  Select the folder where you want to store the program and
            open it.
        g.  Copying the file will begin shortly.  
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(60)  My quartile values don't agree with Minitab.  Is there something wrong with my calculator?
          Probably not.  There is no standard method for calculating quartiles.  The TI calculators use a method by
          Moore and McCabe.  Minitab, I believe,  uses uses a basic Mendehnall and Sincich method but with interpolation rather than
          rounding.

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