Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

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## #1 2013-02-19 05:13:33

{7/3}
Member
Registered: 2013-02-11
Posts: 210

### How do i write it

How do i write this using logic symbols "for all natural number x there exists a unique y such that y is twice as x" ?

There are 10 kinds of people in the world,people who understand binary and people who don't.

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## #2 2013-02-19 07:13:32

muxdemux
Member
Registered: 2012-12-23
Posts: 80

### Re: How do i write it

This could be a way to write it:

Last edited by muxdemux (2013-02-19 07:13:58)

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## #3 2013-02-19 19:35:19

{7/3}
Member
Registered: 2013-02-11
Posts: 210

### Re: How do i write it

When do i use the brackets and what is the meaning of the 2 signs which look like v and upside-down v.

There are 10 kinds of people in the world,people who understand binary and people who don't.

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## #4 2013-02-20 01:00:36

muxdemux
Member
Registered: 2012-12-23
Posts: 80

### Re: How do i write it

The brackets just make it clear which part of the sentence you want the "for all" quantifier to apply. In larger sentences you might want to quantify

for some of the equation but not the rest. I guess in this case the brackets weren't needed.

The 'v' and upside-down 'v' you're talking about sound like the symbols for logical disjunction

and conjunction
, respectively. There's a Wikipedia page which includes all these symbols and describes their meaning if you're interested:

http://en.wikipedia.org/wiki/List_of_ma … al_symbols

(Scroll down about half way for the dis- and conjunction symbols.)

Last edited by muxdemux (2013-02-20 01:04:41)

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