Solution 12093: Displaying Asymptotes on the TI-89 Family, TI-92 Plus, and Voyage™ 200 Graphing Calculators.
How can asymptotes be displayed on the TI-89 family, TI-92 Plus or Voyage 200?
The TI-89 family, TI-92 Plus, or Voyage 200 units do not display asymptotes. The graph application plots a series of points, separated by the number of pixels specified in the "xres" variable on the window screen. As successive points are drawn, they are joined by a line. If two successive points lie on either side of a discontinuity, they will be joined by a line, which may look like a vertical asymptote in some cases (but is simply an artifact of the graphing process).For example, y=(x-2)/(x+3) graphed in the window xMin= -9 and xMax=6.8 will not display the connecting line or "asymptote".
![](https://education.ti.com/images/kbase/c10700ss1.bmp)
Since the function is undefined there, the point is not plotted, and the points immediately to the right and left are not joined by a line. Changing the xMin or xMax values by a small amount will shift the x values that correspond to the plotted points, so that no point will correspond to x = -3 and therefore the "asymptote" will appear.
![](https://education.ti.com/images/kbase/c10700ss2.bmp)
Thus, one can choose the window so that asymptotes do not appear for some (but not all) functions with odd-order poles, but this is almost certainly a waste of effort (even in cases where this is possible, the resulting graph may not show the interesting behavior of the function, for example).
Please see the TI-89 family, TI-92 family and Voyage 200 guidebooks for additional information.