HP 48G Series Quick Start Manual page 76

Note that the three-dimensional coordinate system on the HP 48
1s somewhat constrained compared to its abstract, mathematical
counterpart. Specifically:
The plot display screen does not rotate in space; it always stays
parallel to the zz-plane and perpendicular to the y-axis. This means
that, visually, "height" is always along the z-axis, "width" along the
z-axis, and "depth" along the y-axis.
The y-axis is always oriented so that negative y-values are "nearer"
and positive y-values "farther" away from the plot display.
The eyepoint must be at least one unit "nearer" than y,.qr
(Ye < Ynear — 1) and can never exist "within" the View Volume.
Whenever you move the eyepoint, you also move the plot display
screen so that it remains exactly one unit away in the direction of
the y-axis.
You cannot plot a "top" view of a function (looking down onto the
zy-plane) simply by moving the eyepoint. (You may simulate this
by transforming coordinates, however.)
)
Example: Plot a wireframe view of: f(X,Y) = XY — XY?
Step 1: Change the plot type to Hirafams and enter the function.
DEPMD: Y' STEPS: 8
ENTER INDEPENDENT YAR NAME
EDT [|[OPTS [ERAZE[ORAM]
Step 2: Set the number of horizontal and vertical steps (or "frames")
to plot.
>) 12 ENTER) () 12 ENTER)
PLOT
lief ane : Rad
IRA SEY-RKEY 3!
INDEP: STEPS: 12
DEPMD: YY STEPS: 12
CHOOSE TYPE OF PLOT
[____[choos][OPTS[ERAZE[DRAM]
6-8 Plotting Equations and Analyzing Graphs