HP 49g manual Fast 3D plots, Key simply changes the font in the table from small to big

•	The			key simply changes the font in the table from small to big, and
	vice versa. Try it.
•	The @			key, when pressed, produces a menu with the options: In, Out,
	Decimal, Integer, and Trig. Try the following exercises:
	•	With the option In highlighted, press				. The table is expanded so
		that the x-increment is now 0.25 rather than 0.5. Simply, what the
		calculator does is to multiply the original increment, 0.5, by the zoom
		factor, 0.5, to produce the new increment of 0.25. Thus, the zoom in
		option is useful when you want more resolution for the values of x in
		your table.
	•	To increase the resolution by an additional factor of 0.5 press								,
		select In once more, and press				. The x-increment is now
		0.0125.
	•	To recover the previous x-increment, press						to select
		the option Un-zoom. The x-increment is increased to 0.25.
			@BIG@
	• To recover the original x-increment of 0.5 you can do an un-zoom
		again, or use the option zoom out by pressing						.
			ZOOM
	•	The option Decimal in			produces x-increments of			0.10.
	•	The option Integer in				@@@OK@@@
					produces x-increments of 1.
	• The option Trig in produces increments related to fractions of π , thus
		being useful when producing tables of trigonometric functions.							@ZOOM
	•	To return to normal calculator display press					.
Fast 3D plots					@@@OK@@@

Fast 3D plots are used to visualize@ZOOMOMthree-dimensional@ZOOM`surfaces@ZOUT—@@@OK@@@represented by equations of the form z = f(x,y). For example, if you want to visualize z = f(x,y) = x2+y2, we can use the following:

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