Texas Instruments PLUS TI-89 User Manual

Page 495

478 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 478 of 132

By combining the variations of

part()

, you can

extract all of the sub-expressions in the
simplified result of

expression1

. As shown in

the example to the right, you can store an
argument or operand and then use

part()

extract further sub-expressions.

Note:

When using

part()

, do not rely on any

particular order in sums and products.

part(cos(

pù x+3)) ¸

part(cos(

pù x+3),0) ¸

"cos"

part(cos(

pù x+3),1)! temp ¸

pøx

temp ¸

pøx+3

part(temp,0) ¸

"+"

part(temp) ¸

part(temp,2) ¸

part(temp,1)! temp ¸

pøx

part(temp,0) ¸

"ù "

part(temp) ¸

part(temp,1) ¸

part(temp,2) ¸

Expressions such as (x+y+z) and (xì yì z)
are represented internally as (x+y)+z and
(xì y)ì z. This affects the values returned for
the first and second argument. There are
technical reasons why

part(

x+y+z,1

)

returns

y+x instead of x+y.

part(x+y+z) ¸

part(x+y+z,2) ¸

part(x+y+z,1) ¸

y+x

Similarly, xù yù z is represented internally as
(xù y)ù z. Again, there are technical reasons
why the first argument is returned as yøx
instead of xøy.

part(xù yù z) ¸

part(xù yù z,2) ¸

part(xù yù z,1) ¸

yøx

When you extract sub-expressions from a
matrix, remember that matrices are stored as
lists of lists, as illustrated in the example to
the right.

part([a,b,c;x,y,z],0) ¸

"{"

part([a,b,c;x,y,z]) ¸

part([a,b,c;x,y,z],2)! temp

{x y z}

part(temp,0) ¸

"{"

part(temp) ¸

part(temp,3) ¸

delVar temp

Done

This manual is related to the following products:

PLUS TI-92