Insert paragraph text here.
- Definition 1: sequence
A sequence is a function
gn
gn
defined on the positive integers
'nn'. We often denote a
sequence by
gn
|
n
=1∞
n
1
gn
A real number sequence:
gn=1n
gn
1
n
A vector sequence:
gn=(
sinnπ2
cosnπ2
)
gn
n
2
n
2
A function sequence:
g
n
t={1 if 0≤t<1n0 otherwise
g
n
t
1
0
t
1
n
0
A function can be thought of as an infinite
dimensional vector where for each value of
'tt' we have one
dimension
- Definition 2: limit
A sequence
gn
|
n
=1∞
n
1
gn
converges to a limit
g∈R
g
if for every
ε>0
ε
0
there is an integer N
N such that
∀
i
,i≥N:|gi−g|<ε
i
i
N
gi
g
ε
We usually denote a limit by writing
limit
i
→
∞
gi=g
i
gi
g
or
g
i
→g
g
i
g
The above definition means that no matter how small we
make
εε, except for a
finite number of
g
i
g
i
's, all points of the sequence are within
distance
εε of
gg.
We are given the following convergent sequence:
gn=1n
gn
1
n
(1)
Intuitively we can assume the following limit:
limit
n
→
∞
gn=0
n
gn
0
Let us prove this rigorously. Say that we are given a
real number
ε>0
ε
0
. Let us choose
N=⌈1ε⌉
N
1
ε
, where
⌈x⌉
x
denotes the smallest integer larger than
xx. Then for
n≥N
n
N
we have
|gn−0|=1n≤1N<ε
gn
0
1
n
1
N
ε
Thus,
limit
n
→
∞
gn=0
n
gn
0
Now let us look at the following non-convergent sequence
gn={1 if n=even-1 if n=odd
gn
1
n
even
-1
n
odd
This sequence oscillates between 1 and -1, so it will
therefore never converge.
"My introduction to signal processing course at Rice University."