162 Chapter 10: 3D Graphing
10_3D.DOC TI-89/TI-92 Plus: 3D Graphing (English) Susan Gullord Revised: 02/23/01 11:00 AM Printed: 02/23/01 4:22 PM Page 162 of 2210_3D.DOC TI-89/TI-92 Plus: 3D Graphing (English) Susan Gullord Revised: 02/23/01 11:00 AM Printed: 02/23/01 4:22 PM Page 162 of 22
The viewing angle has three components:
¦
eye
q
— angle in degrees from the
positive x axis.
¦
eye
f
— angle in degrees from the
positive z axis.
¦
eye
ψ
— angle in degrees by which the
graph is rotated counterclockwise
around the line of sight set by
eye
q
and
eye
f
.
In the Window Editor (
Â¥$
),
always enter
eye
q
, eye
f
, and eye
ψ
in
degrees, regardless of the current angle
mode.
Y
Z
X
The view on the Graph screen is always oriented along the viewing
angle. From this point of view, you can change
eye
q
to rotate the
viewing angle around the z axis.
z1(x,y) = (x
3
y
-
y
3
x) / 390 In this example, eye
f
= 70
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
eyeψ Window variable lets you rotate the graph around that
line of sight.
How the Viewing
Angle Is Measured
Note: When
eye
ψ
=0
, the
z axis is vertical on the
screen. When
eye
ψ
=90
,
the z axis is rotated 90
¡
counterclockwise and is
horizontal.
Effect of Changing
eye
q
Note: This example
increments
eye
q
by
30
.
eye
q
eye
f
eye
ψ
Do not enter a
¡
symbol. For example,
type 20, 70, and 0, not 20
¡
, 70
¡
, and 0
¡
.
eye
q
= 20
eye
q
= 50
eye
q
= 80
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