# Interval notation placement

• September 11th 2011, 12:19 PM
cytotoxictcell
Interval notation placement
How do i know how the interval notiation set will be? I have attached a graph for an example =)

like
(5,-3] or is it [-3,5) plus i am confused with the brackets [ ( )]
• September 11th 2011, 01:57 PM
tarheelborn
Re: Interval notation placement
Usually you would write this as {x: -3 < x <= 5} and then then interval notation would be (-3, 5].
• September 11th 2011, 01:59 PM
emakarov
Re: Interval notation placement
It's (-3, 5]. The smaller value (taking the sign into account) must be on the left. The parentheses ( and ) correspond to strict inequalities < and >, while square brackets [ and ] correspond to non-strict inequalities $\le$ and $\ge$.
• September 11th 2011, 02:15 PM
Plato
Re: Interval notation placement
$\begin{gathered}(3,5)\; \equiv \,\left\{ {x:3 < x < 5} \right\} \hfill \\ (3,5]\; \equiv \,\left\{ {x:3 < x \leqslant 5} \right\} \hfill \\ [3,5)\; \equiv \,\left\{ {x:3 \leqslant x < 5} \right\} \hfill \\ [3,5]\; \equiv \,\left\{ {x:3 \leqslant x \leqslant 5} \right\} \hfill \\ \end{gathered}$
• September 12th 2011, 03:00 AM
HallsofIvy
Re: Interval notation placement
Quote:

Originally Posted by Plato
$\begin{gathered}(3,5)\; \equiv \,\left\{ {x:0 < x < 5} \right\} \hfill \\ (3,5]\; \equiv \,\left\{ {x:0 < x \leqslant 5} \right\} \hfill \\ [3,5)\; \equiv \,\left\{ {x:0 \leqslant x < 5} \right\} \hfill \\ [3,5]\; \equiv \,\left\{ {x:0 \leqslant x \leqslant 5} \right\} \hfill \\ \end{gathered}$

Ouch! Plato, what have you been smoking?
• September 12th 2011, 03:12 AM
Plato
Re: Interval notation placement
Quote:

Originally Posted by HallsofIvy
Ouch! Plato, what have you been smoking?

Thanks, corrected!
• September 12th 2011, 03:17 AM
Prove It
Re: Interval notation placement
Quote:

Originally Posted by HallsofIvy
Ouch! Plato, what have you been smoking?

And where can I get some? ;)
• September 12th 2011, 03:41 PM
cytotoxictcell
Re: Interval notation placement
so if something has the infinite symbol '-' <------ similar to that than that symbol is moved to the right?
• September 12th 2011, 08:25 PM
Prove It
Re: Interval notation placement
Quote:

Originally Posted by cytotoxictcell
so if something has the infinite symbol '-' <------ similar to that than that symbol is moved to the right?

What on Earth are YOU smoking, and where can I get some? That's a "minus" or "negative"...

This is infinite... $\displaystyle \infty$
• September 14th 2011, 03:06 PM
cytotoxictcell
Re: Interval notation placement
Quote:

Originally Posted by Prove It
What on Earth are YOU smoking, and where can I get some? That's a "minus" or "negative"...

This is infinite... $\displaystyle \infty$

lol i am not smoking anything =). I just dont know how to make the infinite symbol. How did you do it so that it appears on the forum like you did?
• September 14th 2011, 03:18 PM
Plato
Re: Interval notation placement
Quote:

Originally Posted by cytotoxictcell
lol i am not smoking anything =). I just dont know how to make the infinite symbol. How did you do it so that it appears on the forum like you did?

Use LaTeX tags.
[TEX]\infty[/TEX] gives $\infty$

[TEX](-\infty,0][/TEX] gives $(-\infty,0]$

[TEX](0,\infty)[/TEX] gives $(0,\infty)$