Texas Instruments PLUS TI-89 - Manual (Page 83)

66 Chapter 3: Symbolic Manipulation
03SYMBOL.DOC TI-89/TI-92 Plus: Symbolic Manipulation (English) Susan Gullord Revised: 02/23/01 10:52 AM Printed: 02/23/01 2:12 PM Page 66 of 24
Functions that use delayed simplification have a required var
argument that performs the function with respect to a variable.
These functions have at least two arguments with the general form:
function( expression , var [, ... ] )
For example: solve(x^2 ì x ì 2=0,x)
d (x^2 ì x ì 2,x)
‰ (x^2 ì x ì 2,x)
limit(x с м x ì 2,x,5)
For a function that uses delayed simplification:
1. The var variable is simplified to the lowest level at which it
remains a variable (even if it could be further simplified to a
non-variable value).
2. The function is performed using the variable.
3. If var can be further simplified, that value is then substituted into
the result.
For example:
Delayed Simplification for Certain Built-In Functions
Usually, variables are automatically simplified to their lowest
possible level before they are passed to a function. For certain
functions, however, complete simplification is delayed until
after the function is performed.
Functions that Use
Delayed
Simplification
Note: Not all functions that
use a var argument use
delayed simplification.
Note: You may or may not
want to define a numeric
value for var, depending on
the situation.
Note: The example to the
right finds the derivative of
x
ò at x=5. If x ò was initially
simplified to 75, you would
find the derivative of 75,
which is not what you want.
x cannot be simplified.
x is not simplified. The
function uses x
ò , and
then substitutes 5 for x.
x is simplified to t. The
function uses t
ò .
x is simplified to t. The
function uses t
ò , and
then substitutes 5 for t.