what does this sign means ?

- mathmath333

what does this sign means ?

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- mathmath333

reversed A

- mathmath333

|dw:1435770248432:dw|

- SolomonZelman

for all

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## More answers

- geerky42

\thread

- SolomonZelman

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

- mathmath333

what is thread ?

- SolomonZelman

that means for all real numbers n

- SolomonZelman

for all, that is the meaning

- SolomonZelman

questions?

- geerky42

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

- mathmath333

ok tnx . it means (for all)

- 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.

- SolomonZelman

would*

- SolomonZelman

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

- SolomonZelman

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

- mathmath333

yep i m proud i know it

- SolomonZelman

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

- ganeshie8

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

- mathmath333

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

- ganeshie8

look up quantifiers

- mathmath333

\(0>\sin 0\) ?

- ganeshie8

0 is not a positive real number

- mathmath333

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

- ganeshie8

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

- ganeshie8

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

- mathmath333

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

- mathmath333

ok i see that sign \(\forall\) is from set theory

- mathmath333

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

- ganeshie8

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

- 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

- SolomonZelman

yes, lol, √2

- SolomonZelman

or -√2

- SolomonZelman

... ±√2

- SolomonZelman

(i am using alt shortcuts)

- ganeshie8

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

- mathmath333

what is \(\large \mathbb{Q}\) ?

- ganeshie8

"set" of rational numbers

- mathmath333

there exists no rational numbers that satisfy \(x^2=2\)

- ganeshie8

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

- mathmath333

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

- ganeshie8

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

- ganeshie8

good one!

- mathmath333

yep correct

- mathmath333

it is important to mention stockfish version 6.0

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