Texas Instruments TI-89 사용자 설명서
Symbolic Manipulation
236
Determining If a Variable Is Exists
Determining If a Variable Is Exists
Determining If a Variable Is Exists
Determining If a Variable Is Exists
•
If x is defined, the result may be in a form
you did not expect.
you did not expect.
Note:
When defining a variable, it’s a good
practice to use more than one character
in the name. Leave one-character names
undefined for symbolic calculations.
in the name. Leave one-character names
undefined for symbolic calculations.
Method:
Example:
Enter the variable name.
Use the
isVar()
function.
Unless you knew that
5 had been stored to
x previously, the
answer 75 could be
misleading.
5 had been stored to
x previously, the
answer 75 could be
misleading.
If defined, the variable’s
value is displayed.
value is displayed.
If undefined, the variable
name is displayed.
name is displayed.
If defined, “true” is
displayed.
displayed.
If undefined, “false” is
displayed.
displayed.