## tomiko 2 years ago what does this symbol mean in math? http://i45.tinypic.com/35k200h.jpg

1. tomiko

the V and the other one turned upside down? ?

2. Rudy

The way I've seen it used,V means union of sets and upside down triangle means intersection of sets.

3. tomiko

apparently there's a DIFFERENT meaning :|

4. tomiko

OK i'm leaning this: http://i47.tinypic.com/dxhdm8.jpg. the text means. Set X C R is lower-bounded if:....then that image i posted earlier. in this context what do the V and upside V mean?

5. UnkleRhaukus

$\Large\bigvee_{m\in \mathbb R}\bigwedge_{x\in X}x\geq m$ $$x$$ is greater than or equal to $$m$$ , OR $$m$$ is an element of the real numbers , And $$x$$ is in the set $$X$$ .

6. UnkleRhaukus

$$\land$$ and $$\lor$$ or

7. UnkleRhaukus

$X\subset\mathbb R$ the set $$X$$ is a subset of the real numbers

8. UnkleRhaukus

@Rudy $$A\cup B$$ is the union of sets $$A, B$$ $$A\cap B$$ is the intersection

9. chihiroasleaf

@tomiko I don't understand the language, but it seems 'real analysis' and I guess that it supposed to be, Set $X \subset R$ is bounded from below, or have a lower bound if $\forall m \in R, \exists x \in X, x \ge m$ we can say that, for all m in R, there exist x in X such that x greater than or equal to m, that's the usual symbol that I know... :)

10. tomiko

@chihiroasleaf exactly what i wanted!! thank to @UnkleRhaukus too!!

11. chihiroasleaf

but I think, $X \subset R$ is said to have a lower bound if $\exists m \in R,$ such that $\forall x \in R \rightarrow x \ge m$

12. UnkleRhaukus

the fancy names are conjunctions (and) , disjunction (or)

13. chihiroasleaf

yes.., they usually use for logic, it's my first time see these symbol use in this subject... :D

14. tomiko

but this is NOT logic. i know what they mean in logic. usually the in logic the "v" i smaller. but this one the "V" is very big and under it they write something like x is a member of R. this is definitely not logic.

15. chihiroasleaf

yes.., that's why I say that it's my first time see these symbol are used in this subject, but the definition is a bit different to what I know, may be you can read on this link about upper and lower bound of a set... If I refer to the usual definition of upper and lower bound than, V will mean 'there exist' and '^' will mean 'for all' http://www.emathzone.com/tutorials/real-analysis/upper-and-lower-bounds.html

16. chihiroasleaf

so, your image will mean $\exists m \in R, \forall x \in X, x \ge m$ it will make sense if, we are talking about lower bound... sorry for the mistake...

17. chihiroasleaf

@tomiko