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