hp40g+.book Page 12 Friday, December 9, 2005 1:03 AM

Accessing CAS functions

While you are in the Equation Writer, you can access all

CAS functions, and you can access them in various ways.

General principle: When you have written an expression in the Equation Writer, all you have to do is

press to evaluate whatever you have selected (or the entire expression, if nothing is selected).

How to type Σ and ∫

Press to enter Σ and to enter ∫.

These symbols and are treated as prefix functions with multiple arguments. They are automatically placed before the selected element, if there is one (hence the term prefix functions).

You can move the cursor from argument to argument by pressing or .

Enter the expressions according to the rules of selection explained earlier, but you must first go into selection mode by pressing .

N O T E Do not use the index i to define a summation, because i designates the complex-number solution of x2 + 1 = 0.

Σperforms exact calculations if its argument has a discrete primitive; otherwise it performs approximate calculations, even in exact mode. For example, in both approximate and exact mode:

4

1

= 2.70833333334

∑

----

k = 0

k!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

whereas in exact mode:

 

 

 

 

 

 

1 +

----1

+ ----1

+

----1

+

----1

=

65-----

 

1!

2!

 

3!

 

4!

 

24

Note that Σ can symbolically calculate summations of rational fractions and hypergeometric series that allow a discrete primitive. For example, if you type:

4

1

 

∑ K--------------------------⋅ (K + 1)

K = 1

 

15-12

 

 

Equation Writer