270
RECURSE
This functions is provided for programmers to
let them define functions in the Sequence
aplet.
For example, typing
RECURSE(U,U(N-1)*N,1,2)
U1(N)
seemingly
produces no useful result in the
HOME
view, but would produce the result
shown right in the
SYMB
view of the Sequence aplet. The resulting sequence
is the factorial numbers.
The syntax is:
RECURSE(<seq.name>,<defn of term n>,<1st term>,<2nd term>)
and it must be
ed into a sequence such as
U1,U2..U9,U0
for it to have
any meaning.
Σ
(SUMMATION)
This function, also available on the keyboard, offers a way of calculating the
results of summation notation problems. The syntax of the function is
ordered in the same way as one reads a summation expression (see the
examples below).
Eg. 1
5
2
1
i
i
=
∑
which expands to
2
2
2
2
2
1
2
3
4
5
+
+ +
+
giving an answer of 55,
can be evaluated using
(I=1,5,I
2
)
Eg. 2
6
1
i
i
x
=
∑
where
1
2
3
4
5
6
2,
10,
13,
11,
20,
2
x
x
x
x
x
x
= −
=
=
=
= −
=
can be evaluated by first defining a list
L1
as
{-2,10,13,11,-20,2}
and then calculating
(I=1,6,L1(I))
Note: Although ‘i’ was used as the summation
index in each of the cases above, there
is nothing special about them. ‘i’ and ‘j’
are simply the letters traditionally used
in mathematical problems.
