Texas Instruments TI-89 Manual Book page 582

Using Complex
Variables in
Symbolic
Calculations
Note: For best results in
calculations such as
cSolve() and cZeros() , use
Method 1.
Complex Numbers
and Degree Mode
Note: If you use Degree
angle mode, you must make
polar entries in the form
(rq). In Degree angle
i q
mode, an r e entry causes
an error.
Regardless of the
Complex Format
are treated as real numbers. To perform complex symbolic analysis,
you can use either of the following methods to set up a complex
variable.
Use an underscore _ (
Method 1:
the last character in the variable name to designate a complex
variable. For example:
z_ is treated as a
complex variable
(unless z already
exists, in which case
it retains its existing
data type).
Define a complex variable. For example:
Method 2:
x+yi!z
Then z is treated as a
complex variable.
angle mode is recommended for complex number
Radian
calculations. Internally, the
values to radians, but it does not convert values for exponential,
logarithmic, or hyperbolic functions.
In angle mode, complex identities such as e^(
Degree
sin(q) are not generally true because the values for cos and sin are
i
converted to radians, while those for e^( ) are not. For example,
e^( 45) = cos(45) + sin(45) is treated internally as e^(
i i
cos(p/4) + sin(p/4). Complex identities are always true in
i
angle mode.
mode setting, undefined variables
¥ 
TI.89: TI.92 Plus:
converts all entered trig
TI-89 / TI-92 Plus
Appendix B: Reference Information
2 ) as
q) = cos(q) +
i
45) =
i
Radian
565