Texas Instruments PLUS TI-89 - 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() to
extract further sub-expressions.
Note: When using part() , do not rely on any
particular order in sums and products.
part(cos( pù x+3)) ¸ 1
part(cos( pù x+3),0) ¸ "cos"
part(cos( pù x+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 (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) ¸ 2
part(x+y+z,2) ¸ z
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) ¸ 2
part(xù yù z,2) ¸ z
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]) ¸ 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