## mathmath333 one year ago what does this sign means ?

1. mathmath333

reversed A

2. mathmath333

|dw:1435770248432:dw|

3. SolomonZelman

for all

4. geerky42

5. SolomonZelman

like if you say $$\forall n\in {\bf R}$$

6. mathmath333

7. SolomonZelman

that means for all real numbers n

8. SolomonZelman

for all, that is the meaning

9. SolomonZelman

questions?

10. geerky42

Just my way to saying that @SolomonZelman had it all. No need to get replies from other users

11. mathmath333

ok tnx . it means (for all)

12. SolomonZelman

tnx:) I saw that sign once, never used it tho' because no one qould get it, although it is a good tool to save space.

13. SolomonZelman

would*

14. SolomonZelman

Is that from a tutorial of a person who is obsessed with notations?

15. SolomonZelman

I don't really se it used alot... in any case, you now know it:)

16. mathmath333

yep i m proud i know it

17. SolomonZelman

I clicked on spraguer that I saw just now, and glitched:D

18. ganeshie8

$\forall x\in\mathbb{R^+}~x\gt \sin x$

19. mathmath333

is their any link that gives informtion on all mathmatical signs and its meaning

20. ganeshie8

look up quantifiers

21. mathmath333

$$0>\sin 0$$ ?

22. ganeshie8

0 is not a positive real number

23. mathmath333

oh forget that $$\huge \mathbb{R^{\color{red}{+}}}$$

24. ganeshie8

you may think of $$\forall$$ as a for/foreach loop in a programming language

25. ganeshie8

$\forall x\in \color{red}{X} ~ ~ \color{blue}{\text{statement}}$ the $$\color{blue}{\text{statement}}$$ is applicable to "all" the elements of set $$\color{red}{X}$$

26. mathmath333

i have also just seen reversed E |dw:1435771106226:dw|

27. mathmath333

ok i see that sign $$\forall$$ is from set theory

28. mathmath333

i have seen as "there exist" written as it meaning

29. ganeshie8

$$\exists$$ refers to existence of at least one that satisfies the statement that follows

30. ganeshie8

$\exists x\in \mathbb{R}~:~x^2=2$ means there exists at least one real number $$x$$ "such that" the square of it equals 2

31. SolomonZelman

yes, lol, √2

32. SolomonZelman

or -√2

33. SolomonZelman

... ±√2

34. SolomonZelman

(i am using alt shortcuts)

35. ganeshie8

can you guess what below statement means $\large \not \exists x\in \mathbb{Q}~:~x^2=2$

36. mathmath333

what is $$\large \mathbb{Q}$$ ?

37. ganeshie8

"set" of rational numbers

38. mathmath333

there exists no rational numbers that satisfy $$x^2=2$$

39. ganeshie8

Yes, thats same as saying $$\sqrt{2}$$ is irrational

40. mathmath333

$$\not \exists \mathbb{GM}:\text{GM}:\text{stockfish6.0} ::1:0$$ guess the statement

41. ganeshie8

there doesn't exist a grandmaster who beat the stockfish 1-0

42. ganeshie8

good one!

43. mathmath333

yep correct

44. mathmath333

it is important to mention stockfish version 6.0