The ZTrig Command

Command Summary

Zooms to a trigonometry-friendly window.

Command Syntax


Menu Location


  1. ZOOM to access the zoom menu.
  2. 7 to select ZTrig, or use arrows and ENTER.

Calculator Compatibility


Token Size

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 -47/24πr
  • Xmax=352.5° or 47/24πr
  • Xscl=90° or π/2r
  • 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


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