Convenient screen keys provided
If the definition is recursive but only involves
T
n
−
1
rather than both
T
n
−
1
and
T
n
−
2
then you need not enter a
value for
U1(2)
.
For example, for the sequence
T
n
=
T
n
−
1
+
3;
T
1
=
2
you need only
enter the value
5
into
U1(1)
and the expression
U1(N-1)+4
into
U1(N)
.
The value of
U1(2)
will be ignored in the
SYMB
view but filled in by the
calculator automatically in the
NUM
view.
There are a number of very convenient extra buttons provided at the
bottom of the screen when entering sequences.
- are available as soon as the cursor
moves onto the
U(N)
line (see right). Pressing either will enter the
appropriate text into the sequence definition.
and
Two of these -
The rest become visible once you have begun to enter the sequence
definition.
For example, suppose we enter the Fibonacci sequence into
U2
by defining
U2(N)
as
U2(N-1) + U2(N-2)
.
Rather than having to type all of this we can use the buttons provided, pressing:
This is a very convenient feature, and worth remembering.
There is no
mark next to the definition yet, since the sequence is
defined recursively and no values have yet been given for
U2(1)
and
U2(2)
. Type in a value of
1
for both of these and then press the
NUM
button to switch to the
NUM
view.
As you can see in the screenshot right, the
NUM
view shows the actual
values in the sequence as a table. If you move the highlight into the
U1
and
U2
columns, you can press the
button and see the sequence
rule. You can experiment for yourself and see the result of pressing the
button (see next page for an example). The
button is also
available as usual, but it is easier to use other methods.
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