Texas Instruments PLUS TI-89 - Manual (Page 179)

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 22 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 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 ( ¥ $ ),
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
eye
ψ
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