Texas Instruments PLUS TI-89 - Manual (Page 180)

Chapter 10: 3D Graphing 163
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 163 of 22
By changing eye f, you can elevate your viewing angle above the xy
plane. If 90 < eye f < 270 , the viewing angle is below the xy plane.
z1(x,y) = (x 3 y - y 3 x) / 390 In this example, eye q = 20
The view on the Graph screen is always oriented along the viewing
angles set by
eye q and eye f . You can change eye ψ to rotate the graph
around that line of sight.
z1(x,y)=(x 3 y ì y 3 x) / 390
In this example,
eye q =20 and eye f =70
The eye values are stored in the system variables eye q , eye f , and
eye ψ . You can access or store to these variables as necessary.
TI
-
89 : To type f or ψ , press ¥ c j [F] or ¥ c Ú , respectively.
You can also press 2 ¿ and use the Greek menu.
TI
-
92 Plus : To type f or ψ
, press 2 G F or 2 G Y respectively.
You can also press 2 ¿ and use the Greek menu.
Effect of Changing
eye
f
Note: This example starts
on the xy plane (eye
f = 90)
and decrements eye f by 20
to elevate the viewing angle.
Effect of Changing
eye
ψ
Note: During rotation, the
axes expand or contract to
fit the screen’s width and
height. This causes some
distortion as shown in the
example.
When eye ψ =0 ,
the z axis runs
the height of the
screen.
When eye ψ =90 , the z axis
runs the width of the screen.
As the z axis rotates 90 ¡ , its
range ( ë 10 to 10 in this
example) expands to almost
twice its original length.
Likewise, the x and y axes
expand or contract.
From the Home
Screen or a Program
eye ψ =0
eye ψ =45
eye ψ =90
eye f = 90
eye f = 70
eye f = 50
z=10
z= ë 10
z=10 z= л 10