Texas Instruments Titanium TI-89, User Manual

Page: 375 / 977

3D Graphing 372
For example, suppose you trace the paraboloid z(x,y) = x
2
+ .5y
2
graphed with the
indicated Window variables. You can easily move the cursor to a position such as:
Although the cursor is actually tracing the paraboloid, it appears off the curve because
the trace coordinates:
•
xc
and
yc
are within the viewing cube.
– but –
•
zc
is outside the viewing cube.
Note:
QuickCenter lets you center the viewing cube on the cursor’s location. Simply
press
¸
.
When
zc
is outside the z boundary of the viewing cube, the cursor is physically displayed
at
zmin
or
zmax
(although the screen shows the correct trace coordinates).
Rotating and/or Elevating the Viewing Angle
In 3D graphing mode, the
eye
q
and
eye
f
Window variables let you set viewing angles that
determine your line of sight. The
eye
ψ
Window variable lets you rotate the graph around
that line of sight.
Trace cursor
Valid trace
coordinates