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Math Help - How to write propositions into symbolic forms

  1. #1
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    Exclamation How to write propositions into symbolic forms

    Well I was wondering if there is a method which some one follows to solve questions like these..

    Here is an example

    The square of every real number is a non-negative number

    (for all x)(x element of Z) --> (x^2>0)

    is this how you write it ? btw I used A upside down for (for all x)

    if you can kindly post any websites that teaches how to master this

    Thanks
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  2. #2
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    http://en.wikipedia.org/wiki/Set_(mathematics)

    this is what I founded in 1 min., just google it... and you will find what you want.
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  3. #3
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    Introduction to Logic

    Hello Khonics89
    Quote Originally Posted by Khonics89 View Post
    Well I was wondering if there is a method which some one follows to solve questions like these..

    Here is an example

    The square of every real number is a non-negative number

    (for all x)(x element of Z) --> (x^2>0)

    is this how you write it ? btw I used A upside down for (for all x)

    if you can kindly post any websites that teaches how to master this

    Thanks
    You have nearly got it right. We usually use \mathbb{R} to denote the real numbers, and 'non-negative' means 'greater than or equal to zero'. So the correct answer would be:

    \forall x [(x\in\mathbb{R}) \Rightarrow (x^2 \ge 0)]

    If you want some on-line material that introduces Logic to a beginner, you'll find some notes (with lots of worked examples and exercises) that I wrote for Wikibooks starting just here. And in particular, the use of quantifiers is covered just here.

    Grandad
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