Temporary storage of anti-derivative expressions used during CAS operations.
Temporary storage of a matrix used during CAS operations.
Temporary storage of graphic display during step-by-step operations.
Points to note when choosing settings
The CAS is a powerful tool, and part of that power lies in the many modes and settings available. This means
that if a setting is wrong then the CAS can give unexpected results or error messages. The following points
should be observed. If an unexpected error occurs, or an unexpected message is seen, check this list.
Many CAS commands will give numeric results instead of symbolic results if numeric mode is set
instead of being cleared. Though these results may be correct, they will not be what the user wants if a
symbolic result is needed. For this reason, the Flags section of most operation descriptions says that
numeric mode should not be set.
If approximate mode is set instead of exact mode, CAS commands will often give reasonable results,
but unexpected results can be obtained, because, for example, powers are real numbers, not integers,
for instance a cube will be treated as x
operation descriptions says that exact mode should be set. Some commands, like the numeric solvers,
will only find approximate solutions if approximate mode is set.
CAS operations are designed to work with integers if possible, and some CAS operations round their
inputs before using them. FIX 0 mode will round to whole numbers, losing accuracy. STD mode will
retain full accuracy, so it is the best display mode to use with the CAS and is used in most of the
examples in this chapter.
For the same reasons, the general solutions, symbolic constants and symbolic arguments flags (flags –1,
–2 and –3) should normally be clear when working with the CAS.
Where possible, integer numbers should be used as input, not real numbers. The functions RND,
CEIL and FLOOR can round a real number to a whole real number, and R$I will convert a whole
real number to an integer.
If complex inputs are given, approximate mode may need to be set to find solutions, and complex
mode must be set (flag –103 set).
Not only the trigonometry rewriting operations, but some other CAS operations require the angle
mode to be set to radians (flag –17 clear), even if it is not immediately obvious that this is so. For this
reason, the Flags section of many operation descriptions says that radians mode should be set.
Some CAS operations will work one step at a time if step-by-step mode is set (flag –100 set). If a result
is wanted immediately, and the calculator instead displays one step of the operation, cancel the
operation, clear flag –100, then repeat the operation.
If a mode needs to be changed for an operation to work, the calculator will by default ask if the mode
can be changed. If the Silent mode switch flag (flag –120) is set, the calculator changes the mode
without asking. If the mode switch disallowed flag (flag –123) is set, the mode will not be changed and
an error will occur.
All the system flags from –99 to –128 are intended for use by the CAS. It is worth reading Appendix C
in the User's Guide to learn the detailed effects of these flags on CAS operations and displays.
Remember that in RPN mode, symbolic expressions typed on the command line should be enclosed in
single quote marks 'x + y'. For clarity, it can be helpful to type expressions in single quote marks in
Algebraic mode too.
It is important to write symbolic expressions using the current variable. Some CAS operations will
work with this variable, but treat other variables simply as unknown numbers. If an expression has
been entered using a variable other than the current variable, it may be simpler to change the current
variable in the CAS MODES form, rather than rewrite the whole expression.
In algebraic mode (flag –95 set), some CAS commands will replace variables with their numeric values
before returning a result, even if "argument to symbolic" mode is set (flag –3 clear). In RPN mode,
instead of x
. For this reason, the Flags section of most
Computer Algebra Commands 4-3