Texas Instruments TI-89, TI-92

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() to

extract further sub-expressions.

Note: When using part(), do not rely on any

particular order in sums and products.

part(cos(pùx+3)) ¸1

part(cos(pùx+3),0) ¸"cos"

part(cos(pùx+3),1)!temp ¸

3+pøx

temp ¸pøx+3

part(temp,0) ¸"+"

part(temp) ¸2

part(temp,2) ¸3

part(temp,1)!temp ¸pøx

part(temp,0) ¸"ù"

part(temp) ¸2

part(temp,1) ¸p

part(temp,2) ¸x

Expressions such as (x+y+z) and (xìyìz)

are represented internally as (x+y)+z and

(xìy)ìz. 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) ¸2

part

(

x+y+z,2

)

part

(

x+y+z,

y+x

Similarly, xùyùz is represented internally as

(xùy)ùz. Again, there are technical reasons

why the first argument is returned as yøx

instead of xøy.

part(xùyùz) ¸2

part

(

xùyùz,2

)

part

(

xùyùz,

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]) ¸2

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

{x y z}

part(temp,0) ¸"{"

part(temp) ¸3

part(temp,3) ¸z

delVar temp ¸Done