To install click the Add extension button. That's it.

The source code for the WIKI 2 extension is being checked by specialists of the Mozilla Foundation, Google, and Apple. You could also do it yourself at any point in time.

Kelly Slayton
Congratulations on this excellent venture… what a great idea!
Alexander Grigorievskiy
I use WIKI 2 every day and almost forgot how the original Wikipedia looks like.
Live Statistics
English Articles
Improved in 24 Hours
Added in 24 Hours
Show all languages
What we do. Every page goes through several hundred of perfecting techniques; in live mode. Quite the same Wikipedia. Just better.

Disjunction elimination

From Wikipedia, the free encyclopedia

In propositional logic, disjunction elimination[1][2] (sometimes named proof by cases, case analysis, or or elimination), is the valid argument form and rule of inference that allows one to eliminate a disjunctive statement from a logical proof. It is the inference that if a statement implies a statement and a statement also implies , then if either or is true, then has to be true. The reasoning is simple: since at least one of the statements P and R is true, and since either of them would be sufficient to entail Q, Q is certainly true.

An example in English:

If I'm inside, I have my wallet on me.
If I'm outside, I have my wallet on me.
It is true that either I'm inside or I'm outside.
Therefore, I have my wallet on me.

It is the rule can be stated as:

where the rule is that whenever instances of "", and "" and "" appear on lines of a proof, "" can be placed on a subsequent line.

YouTube Encyclopedic

  • 1/3
    8 025
    6 483
    1 149
  • Disjunction Elimination example
  • Disjunction elimination and introduction
  • Question 8 - Using Disjunction Elimination.mp4


Formal notation

The disjunction elimination rule may be written in sequent notation:

where is a metalogical symbol meaning that is a syntactic consequence of , and and in some logical system;

and expressed as a truth-functional tautology or theorem of propositional logic:

where , , and are propositions expressed in some formal system.

See also


  1. ^ "Archived copy". Archived from the original on 2015-04-18. Retrieved 2015-04-09.CS1 maint: archived copy as title (link)
  2. ^
This page was last edited on 26 December 2020, at 16:47
Basis of this page is in Wikipedia. Text is available under the CC BY-SA 3.0 Unported License. Non-text media are available under their specified licenses. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. WIKI 2 is an independent company and has no affiliation with Wikimedia Foundation.