331
4) Don’t use a summation variable of lower-case i. This is assumed by the
CAS to be the unit imaginary value - the root of x
2
+1=0.
5) Although you can use the integration symbol provided on the keyboard it
has disadvantages outlined on page 82. Use the INTVX function instead.
See the example on page 320.
6) The COLLECT function referred to earlier will factorize over the set of
integers. For example, COLLECT(x
2
-4) will result in (x+2)(x-2),
whereas COLLECT(X
2
+4) will result in X
2
+4 back again.
On the other hand the FACTOR function will factorize over the irrational
and complex sets too. Entering FACTOR(X
2
+2) will result in the
expression
()()
22
ix i+−.
7) The infinity symbol can be found in the Constants section of the MATH
menu but can also be obtained by pressing SHIFT 0. Pressing (-) first
will produce -∞, while pressing (-) twice will give +∞. These are often
needed for use in the LIMITS function.
For example, evaluating LIMIT(
xx x++ −,+∞) will give ½ (after
a very long wait).
As with the infinity symbol there is also a shortcut for the symbol i. Just
press SHIFT 1.
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