HP 39gs VS TI-83 FEATURES & DIFFERENCES PART 3

Graphing

There are 4 graph modes (Function Parametric Polarl Sequences). These modes all occupy the same screen key / window and therefore only one form at a time can have graphs drawn and parameters. You must place the calculator in the appropriate graph mode using [MODE]. Graphs: Function definition; To enter the rule for a function to be graphed, press the[Y=] key. The corresponding key on the HP38 is [SYMB].
Cartesian Functions : Plotting Graphs : Scaling Axis

Place the calculator in the Cartesian graph mode using [MODE] [Func] (This is the default mode). Up to ten Graphs (Functions) can be stored in Y1=; Y2=; ... Y9=; Y0=. Select from Yl=; Y2=; ... Y9=; Y0= Input your function definition. Long equations will wordwrap. Only those graphs with the = sign shaded will be plotted. Use the [X / 0 / T / N] to enter the variable x. The TI-83 is superior in graph styles (graphing regions - shading). Resolution (1-8 on TI-83) which is the same as the choice Faster-Detail on HP 39gs) but the resolution on the HP38 is superior. (For example check the plotting of a unit circle on both calculators). Press [Trace] to include display of equations on graph The equation of the current graph is displayed when you switch between graphs. This is much the same as for the HP 39gs.

Scaling Axis

TI38 Setting scales:. Press [WINDOW] then set the desired scaling features. This is much the same as for the HP 39gs To pause a plot which is in progress press [ENTER]. To stop the graphing press ON You must wait for a graph to complete or stop before you can go on to another action. The HP 39gs does this using a more visible Screen menu option [PAUSE]. Axes labels on the TI-83 are not satisfactory: no numeric scale is shown onscreen, and the variables x, and y are poorly placed in relation to the axes. The HP 39gs allows both the naming of the axes as well as placing the numerical scaling on the axes. In the [GRAPH] window by using [2nd] [CALC] with 1Value to obtain the x coordinate of any point on a plotted graph, press I ENTER I to move the cursor to that point on the currently selected graph. The coordinates of the point are given onscreen. However it is a little more difficult to obtain the slope of the curve at precise points as this depends upon the scaling options chosen. Using [2nd][CALC] 5 dy / dx.

With the HP 39gs the slope feature can easily be used to determine the gradient function associated with any graph. Used with Makelist and combined with the fact that the HP can graph the derivative of any plotted function, students can gain excellent insight into the process of differentiation

Table of values: The HP 39gs more versatile in the table mode as you can ask for any value while you are in table mode and the whole table scrolls to that value.

With the TI-83 you must either set the table at the required value or else set tabiset to ask rather than Auto but this loses the scrollable table aspect. For example if you wish to find f(x) when x = 23 to determine f(23) on the HP 39gs place the cursor in the left (x) column then enter 23 and the whole table jumps to this value. However on the TI you must either scroll down to the value 23, or press [2nd][CALC][TBLSET] and enter the required x value of 23 or else select the Ask option. If this last option is used you do not get the table for the nearby values.

TI-83: Table of values, yes but you must scroll to values. User is single value only, not as easy to do limits. Zoom feature in table mode is not available on the TI-83, but this is a feature offered on HP 39gs. If studying Limits, the fact that the HP 39gs permits one to use the Zoom feature while in the Table (NUM) mode, by setting the zoom factor to 10 or any power of 10 this enables students to study limits numerically. This Table zoom feature for the study of limits is not available on the TI-83.

Zoom features offered in Graph mode are roughly the same for both TI-83 and HP 39gs.

Screen Scroll in the graph window: Yes (but all the calculators at this level are slow with this). Shading for inequalities Yes [2nd][DRAW] (Cartesian only) Y2.

2nd][CALC] offers seven features such as: Value, Zero; Max; Min: Intersection etc These are offered on both the TI and the HP 39gs (With the HP this is a screen menu option offered in the PLOT window as these are features that are related to the graph of the function being considered). Split screen with scroll table and switch between functions in Column. Both TI and HP do the same in this respect.

TI-83 Feature: Choice of 5 line styles for graphs is available. This can be a very useful feature.

Use [2nd] [Catalog] key to gain access to a listing of all the functions offered on the TI. I feel it would be just as quick to type in your function, as it would be to locate and edit the relevant function.

Plotting Graphs of, Parametric Functions or Polar Functions or Plotting Sequences

You must place the calculator in the appropriate graph mode using [MODE]. Default setting is that of the last graphing done (Whether in Cartesian or polar previously). HP 39gs lets you set up your plotting parameters in each plot type Function; Parametric; Polar; or Sequences. This is due to the Aplet structure unique to the HP 39gs.

TI-83 permits you to plot six parametric sets X1T.,Y1T= to X6T=,Y6T=. Use [WINDOW] to set up the graphing (scaling) options.

HP 39gs has 10 such parametric sets and if more are required they can be set up in their own Aplet.
TI-83 permits you to plot six Polar Functions of the form (R,0). You must place the calculator in the appropriate graph mode using [MODE] [WINDOW] to set up the graphing (scaling) options. HP 39gs has 10 such Polar Plots and if more are required they can be set up in their own Aplet.

TI-83 permits you to plot three sequences u(n); v(n) and w(n). To plot Sequences you must place the [MODE] select [Seq] [u] [ENTER]. Note n must be entered using the [XT0n] key.

The sequence function u(n) must be entered using the key sequence [2nd][u][XT0n] similarly for the other two sequences v(n) and w(n).

HP 39gs has 10 such Sequence Plots. I also feel that the HP enters sequences better by using screen menus. Also with HP if you input the formulae for the Nth term both terms 1 and 2 are automatically inserted.
On the TI-83 Term n is restricted to the the nMax set in [WINDOWS] and this must be changed if you want higher or lower values.

The TI-83 does enable sequences to be defined recursively, using lists, but the HP does the input more simply using the screen menu keys.

Draw Feature

On the TI-83, the tangent drawing facility is useful You can draw the tangent at a point on the curve. Select 5Tangent from [2nd] [DRAW] .Press [ENTER] to put you back in the graph window. Input the appropriate x-value I ENTER) the tangent is drawn on the graph and the equation of the tangent is given on screen. Diagrams drawn using DRAW is removed if you rescale your graph screen. I feel there is too much changing between screens.

Text can be included with diagrams but it is a little clumsy and difficult to label a figure. On the TI-83 Graphs & Diagrams can be saved to any of the ten memories Pict 1 to Pict0, these can be recalled but are drawings (Pictures) only and not functions therefore tracing is not possible.

Shaded regions for inequalities are superior on the TI-83 when compared to the HP 39gs. Most of the draw features are better done on a computer with appropriate software.

Graphs and settings can be saved to any of ten memories G_Datal to G_Data0. These can be recalled. This compares poorly with the aplet feature of the HP 39gs where the Aplet structure allows the user to save up to 10 of each of Function; Parametric; Polar; Sequences together with notes and diagrams associated with each Aplet.