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Appendix A: Functions and Instructions 423
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 423 of 132
cos()
TI
-
89
:
2X
key TI
-
92 Plus:
X
key
cos(
expression1
)
⇒
expression
cos(
list1
)
⇒
list
cos(
expression1
)
returns the cosine of the
argument as an expression.
cos(
list1
)
returns a list of the cosines of all
elements in
list1
.
Note: The argument is interpreted as either a
degree or radian angle, according to the
current angle mode setting. You can use
ó
or
ô
to override the angle mode
temporarily.
In Degree angle mode:
cos((p/4)
ô
)
¸
‡
2
2
cos(45)
¸
‡2
2
cos({0,60,90})
¸
{1 1/2 0}
In Radian angle mode:
cos(p/4)
¸
‡
2
2
cos(45¡)
¸
‡2
2
cos(
squareMatrix1
)
⇒
squareMatrix
Returns the matrix cosine of
squareMatrix1
.
This is
not
the same as calculating the cosine
of each element.
When a scalar function f(A) operates on
squareMatrix1
(A), the result is calculated by
the algorithm:
1. Compute the eigenvalues (
l
i
) and
eigenvectors (V
i
) of A.
squareMatrix1
must be diagonalizable.
Also, it cannot have symbolic variables
that have not been assigned a value.
2. Form the matrices:
B =
l
1
0
… 0
0
l
2
… 0
0
0
… 0
0
0
…
l
n
and X = [V
1
,V
2
, … ,V
n
]
3. Then A = X B X
ê
and f(A) = X f(B) X
ê
. For
example, cos(A) = X cos(B) X
ê
where:
cos (B) =
cos( )
cos( )
cos( )
λ
λ
λ
1
2
00
00
00 0
00
K
K
K
K
n
All computations are performed using
floating-point arithmetic.
In Radian angle mode:
cos([1,5,3;4,2,1;6,
ë
2,1])
¸
.212… .205… .121…
.160… .259… .037…
.248…
ë
.090… .218…