# Show that the sequence is bounded.

• Apr 5th 2010, 06:55 PM
WartonMorton
Show that the sequence is bounded.
I know that is has to be bounded because its finite, but I'm guessing there is some sort of mathematical proof for this?
• Apr 5th 2010, 07:21 PM
Drexel28
Quote:

Originally Posted by WartonMorton
I know that is has to be bounded because its finite, but I'm guessing there is some sort of mathematical proof for this?

Bounded in what sense? That the diameter of the set is finite? This would follow since $\Omega=\left\{|a_k-a_j|:a_k,a_j\in S,\text{ }j\ne k\right\}$ is finite and each element is a finite number and thus $\text{diam }S=\max\text{ }\Omega<\infty$
• Apr 5th 2010, 07:33 PM
WartonMorton
Quote:

Originally Posted by Drexel28
Bounded in what sense? That the diameter of the set is finite? This would follow since $\Omega=\left\{|a_k-a_j|:a_k,a_j\in S,\text{ }j\ne k\right\}$ is finite and each element is a finite number and thus $\text{diam }S=\max\text{ }\Omega<\infty$

I think that is a little advance. We have not talked about diameters of sequences in class. I think what they mean by bounded is something along the lines of like S= {1, 2, 3, ... , 10} where it is bound by 1 and 10.
• Apr 5th 2010, 07:40 PM
Drexel28
Quote:

Originally Posted by WartonMorton
I think that is a little advance. We have not talked about diameters of sequences in class. I think what they mean by bounded is something along the lines of like S= {1, 2, 3, ... , 10} where it is bound by 1 and 10.

Well you still haven't defined what you mean by bounded.
• Apr 5th 2010, 07:44 PM
WartonMorton
Quote:

Originally Posted by Drexel28
Well you still haven't defined what you mean by bounded.

bounded in the sense of a bounded set..?
• Apr 5th 2010, 07:48 PM
Anonymous1
What Drexel28 is trying to say is...

Assume that $S$ is finite but not bounded above.

Set $max\{S\}=m_0,$ but then the set is bounded by $m_0.$

Therefore, there must be some $m_1\in S: m_1 > m_0,$ but then the set is bounded by $m_1$... ad infinitum.

The set must be infinite to be unbounded.

A similar argument shows the set is bounded below...