Texas Instruments Titanium TI-89, User Manual

Page: 780 / 977

Appendix A: Functions and Instructions 777
You should also use
var
_ for any other variables in
equation
that might have unreal values. Otherwise,
you may receive unexpected results.
cSolve(conj(z)=1+ i ,z) ¸
z=1+ i
z_ is treated as complex:
cSolve(conj(z_)=1+ i ,z_)
¸
z_=1
−
i
cSolve(
equation1
and
equation2
[ and
…
] ,
{
varOrGuess1
,
varOrGuess2 [
,
… ]
})
⇒
Boolean expression
Returns candidate complex solutions to the
simultaneous algebraic equations, where each
varOrGuess
specifies a variable that you want to
solve for.
Optionally, you can specify an initial guess for a
variable. Each
varOrGuess must have the form:
variable
– or –
variable
=
real or non
-
real number
For example,
x
is valid and so is
x=3+
i .
If all of the equations are polynomials and if you do
NOT specify any initial guesses,
cSolve()
uses the
lexical Gröbner/Buchberger elimination method to
attempt to determine
all complex solutions.
Note: The following examples use an
underscore _
@ ¥ q
H 2 q
so that the variables will be
treated as complex.
Complex solutions can include both real and non-
real solutions, as in the example to the right.
cSolve(u_
ù
v_
ì
u_=v_ and
v_^2=
ë
u_,{u_,v_})
¸
u_=1/2 +
3
2
ø
i and v_=1/2
ì
3
2
ø
i
or u_=1/2
ì
3
2
ø
i and v_=1/2 +
3
2
ø
i
or u_=0 and v_=0
Simultaneous polynomial equations can have extra
variables that have no values, but represent given
numeric values that could be substituted later.
cSolve(u_
ù
v_
ì
u_=c_
ù
v_ and
v_^2=
ë
u_,{u_,v_})
¸
u_=
ë
( 1
ì
4
ø
c_+1)
2
4
and v_=
1
ì
4
ø
c_+1
2
or
u_=
ë ( 1
ì
4
ø
c_
ì
1)
2
4
and v_=
ë ( 1
ì
4
ø
c_
ì
1)
2
or u_=0 and v_=0
You can also include solution variables that do not
appear in the equations. These solutions show how
families of solutions might contain arbitrary
constants of the form @
k, where
k
is an integer
suffix from 1 through 255. The suffix resets to 1
when you use
ClrHome
or
ƒ
8:Clear Home
.
For polynomial systems, computation time or
memory exhaustion may depend strongly on the
order in which you list solution variables. If your
initial choice exhausts memory or your patience, try
rearranging the variables in the equations and/or
varOrGuess
list.
cSolve(u_
ù
v_
ì
u_=v_ and
v_^2=
ë
u_,{u_,v_,w_})
¸
u_=1/2 +
3
2
ø
i and v_=1/2
ì
3
2
ø
i
and w_=@1
or
u_=1/2 ì
3
2
ø i and v_=1/2 +
3
2
ø i
and w_=@1
or u_=0 and v_=0 and w_=@1