Zooms to a trigonometry-friendly window.

ZTrig

Press:

- ZOOM to access the zoom menu.
- 7 to select ZTrig, or use arrows and ENTER.

TI-83/84/+/SE

1 byte

The `ZTrig` command sets the screen to a special friendly window useful for trigonometric calculations. Unlike the `ZDecimal` and `ZInteger` commands, for which the distance between two pixels is a short decimal or integer, `ZTrig` sets the horizontal distance between two pixels to be π/24 (in `Radian` mode) or 7.5 (in `Degree` mode) . The specific changes `ZTrig` makes are:

- Xmin=-352.5° or -47/24π
^{r} - Xmax=352.5° or 47/24π
^{r} - Xscl=90° or π/2
^{r} - Ymin=-4
- Ymax=4
- Yscl=1

Although this window is not quite square (and therefore, distances in the X and Y direction are not exactly equally proportioned), it is quite close, when in `Radian` mode. In a square window (such as the output of `ZSquare`), Ymax would have to be 31/24π, which is approximately 4.05789. As you can see, the value of 4 that `ZTrig` uses is not too far off.

# Advanced Uses

In theory, `ZTrig` should be quite useful in graphing trigonometric functions, since the calculated points would fall exactly on important angles; for example, it would graph the asymptotes of Y=`tan(`X) correctly. This is actually only true when in `Degree` mode. In `Radian` mode, due to round-off error, the pixels far away from the origin do not *exactly* correspond to rational multiples of π. For example, the pixel which was supposed to correspond to π/2 actually has a value of .5000000001*π, which is enough to make this command mostly useless.

However, in `G-T` mode, the size that the graph takes up on the screen is different, and `ZTrig` uses the same values, unlike `ZDecimal`.

# Error Conditions

**ERR:INVALID**occurs if this command is used outside a program (but not if the menu option is used, of course).

# Related Commands

# See Also

.