Thursday, May 23, 2013

Simple Proposition

Introduction for simple proposition:

A simple proposition is a statement, which in the given context is either true or false but not both. The simple propositions are denoted by small letters p, q, r …

Examples:

Sum of two even integers is even integer.

`sqrt(3)` is a rational number.

Earth is flat.

7 is a prime number.

5 – 7 = -2.

Note: The statements involving opinions, question marks, exclamatory mark, command. Wish is not propositions.

Examples for simple proposition:

Logic is interesting.

What a beautiful weather!

Where are you going?

Pleas sit down.

May god bless you?


Concept - simple proposition:

Truth-value in simple proposition:

The truthiness or falsity of a proposition is called its truth-value. If a proposition is true it is denoted by “T” and if it is false it is denoted by “F.”

Example: The truth-value of

5 + 6 = 11 is “T.”

“Today is Sunday” is either “T” or “F” in the given context i.e., on a particular day it is only one of “T” or “F.”

Use of simple proposition:

Logical Connectives and Compound Propositions:

Two or more simple propositions are connected by using the words “and”, “or”, “if … then”, “if and only if”. These words or phrases are called logical connectives. Any proposition containing one or more connectives is called a compound proposition. The simple propositions occurring in a compound proposition are called its components.

Truth table:

The truth-values of the compound proposition for all possible truth-values of its components are expresses in the form of a table called truth table.

For a compound proposition with only one simple proposition, truth table consists of 2 possibilities (either T or F).

For a compound proposition with two proposition truth table consists of `2^2` = 4 possibilities. For a compound proposition with 3 propositions truth table consists of  `2^3` = 8 possibilities.

Is this topic Greatest Integer Function hard for you? Watch out for my coming posts.

Example for simple proposition:


Write the following simple propositions in symbols:

An integer is even if and only if it is divisible by 2.

Solution:

Let       p: An integer is even.

q: It is divisible by 2.

The given proposition is p`<=>`q.

If 6+3 =7, then 7-3=6

Solution:

Let       p: 6+3=7

q: 7-3=6

Then the given proposition is p`=>`q.

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