# Math Help - Unfamiliar use of interval brackets

1. ## Unfamiliar use of interval brackets

Hey, I was wondering if anyone could clear up for me what would generally be meant when you say that a certain value has to

"lie within the strip ] x , y ["? What exactly does it signify when the brackets are in the opposite direction as compared to how you would indicate a closed interval from x to y, [x,y]?

2. ## Re: Unfamiliar use of interval brackets

Originally Posted by Scurmicurv
Hey, I was wondering if anyone could clear up for me what would generally be meant when you say that a certain value has to
"lie within the strip ] x , y ["? What exactly does it signify when the brackets are in the opposite direction as compared to how you would indicate a closed interval from x to y, [x,y]?
That notation is unusual but not unheard of.
$]a,b[=\{x: a,
$]a,b]=\{x: a ,
etc.

3. ## Re: Unfamiliar use of interval brackets

Aha, so it's just an open interval? Thanks, that helps a lot to get that cleared up!