# on the TI-89

## The "Magic Number" = 158

You would like to know the slope of the graph at 2.0, but the cursor skips from 1.997082 to 2.001456! There's got to be a way to get the cursor to use "nice" numbers! Yes, there is a way, and it's easy.

 All you need to do is insure that each pixel represents a "nice" increment - 1, 0.1, 0.01, etc. To do this, you just have to multiply this increment by the width of the screen in pixels, 158. In the example shown at right, the left edge (xmin) of the screen will be at x = -5, and the screen cursor will skip by a "nice" number. Of course, you have to adjust the xmin value and the increment to get the interesting portion of the graph on the screen, which might take a little trial and error or calculation. Note: If you also change xres to 1, then the cursor will skip by your increment value. In this example, the cursor increment will be 2*0.1 = 0.2, but if you change xres to 1, the cursor increment will be 0.1 .

last update November 26, 2006 by JL Stanbrough