Texas Instruments TI-89 - Page 553

536 Appendix A: Functions and Instructions
8992APPA.DOC TI-89 / TI-92 Plus: Appendix A (US English) Susan Gullord Revised: 02/23/01 1:48 PM Printed: 02/23/01 2:21 PM Page 536 of 132
¡
, ', "
2“
key
(
¡
),
2È
key
('),
2É
key
(")
dd
¡
mm
'
ss.ss
"
⇒
expression
dd
A positive or negative number
mm
A non-negative number
ss.ss
A non-negative number
Returns
dd
+(
mm
/60)+(
ss.ss
/3600).
This base-60 entry format lets you:
•
Enter an angle in degrees/minutes/seconds
without regard to the current angle mode.
•
Enter time as hours/minutes/seconds.
In Degree angle mode:
25°13'17.5"
¸
25.221
...
25°30'
¸
51/2
'
(prime)
2È
key
variable
'
variable
''
Enters a prime symbol in a differential
equation. A single prime symbol denotes a
1st-order differential equation, two prime
symbols denote a 2nd-order, etc.
deSolve(y''=y^(
ë
1/2) and
y
(
0
)
=0 an
d
y'
(
0
)
=0,t,y
)
¸
2
ø
y
3/4
3
=t
_
(underscore)
TI
-
89:
¥

key TI
-
92 Plus:
2
key
expression
_
unit
Designates the units for an
expression
. All
unit names must begin with an underscore.
You can use pre-defined units or create
your own units. For a list of pre-defined
units, refer to the chapter about constants
and measurement units in this book. You
can press:
TI-89:
2
9
TI-92 Plus:
¥À
to select units from a menu, or you can
type the unit names directly.
3_m
4 _ft
¸
9.842…
ø
_ft
Note: To type
4
, press
2

.
variable
_
When
variable
has no value, it is treated as
though it represents a complex number. By
default, without the _
, the variable is
treated as real.
If
variable
has a value, the _ is ignored and
variable
retains its original data type.
Note: You can store a complex number to
a variable without using _
. However, for
best results in calculations such as
cSolve()
and
cZeros()
, the _ is recommended.
Assuming z is undefined:
real(z)
¸
z
real(z_)
¸
real(z_)
imag(z)
¸
0
imag(z_)
¸
imag(z_)