Category Archives: TI-89

3D graphing on TI Nspire and TI-89 Titanium

The TI Nspire provided a very rich set of 3D graphing capability including function and parametric plotting. Thanks to the hardware upgrade from its predecessor, the real time rotation and animations are more than satisfying most of the time. Samples below can be created and visualized on the Nspire with a few inputs. It is quite nostalgic to see these wireframes for us who had been through the 90s when CAD software was in its infancy on the road to being readily commercialized!3dnspire

Speaking of the predecessors of the Nspire, the Titanium is the first to offer built-in 3D plotting capability in the TI lines of calculators. To this day I still find it interesting to plot some surface that it seems impossible to plot in the Nspire, like the combinatorics function shown below. The same function in the 3D graph on TI Nspire simply resulted in syntax error, but is evidently possible on the Titanium, not only with a functioning plot as shown in graph below, but also the correct trace values in the graph trace function.

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The following window setting is the optimal for such graph.

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Date arithmetic in TI Nspire

The TI Nspire CX (and also 83, 84, 89 series) provided a useful date function, dbd(), for finding the number of days between two input dates. However, after nothing turn up searching for function to perform days addition, a quick and dirty program is developed by taking advantage of this built-in function.

The program takes two parameters: a date and the number of day to add, and basically brute force a range of dates to check if the dbd() function returns a value equals that of the intended number of days to add. The program assumed the format DDMM.YY, while the built-in dbd() function accepts format in either DDMM.YY or MM.DDYY.

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Conversion of system mode settings from Nspire to TI-89

Mode settings can be done on both the Nspire and TI-89 using the setMode() call. After finding out the parameters and values differ significantly when porting TI-BASIC program from the Titanium to the Nspire, a chart showing the corresponding TI-89 values will be handy. The Titanium required string type for the arguments in the setMode() call.

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Some mode setting options available in the Titanium seem to be absent in the Nspire.