## Example of a Harder Sentential Proof

## Example of a Harder Propositional Proof

2/27/06

Topic

Logical System

2/27/06

Topic

Logical System

12/23/05

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Topic

Logical System

2/24/06

Topic

Logical System

9/12/06

This video shows the techniques for Conditional Proof using the downloadable application Deriver. But the techniques are exactly the same for the Proof applet running in a web page. So, the video may look slightly different to what you are looking at, but the underlying principles and approach are the same.

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Topic

Logical System

12/22/05

This video is set in the context of the downloadable program, but it applies equally well in the setting of a proof applet.

Topic

Logical System

Topic

Logical System

2013

This movie shows the downloadable application being used, but the manipulations are so similar to those of the web page applet that it really covers both.

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Topic

Logical System

2013

To learn how to use the Universal and Existential Quantifiers in symbolizing propositions.

In Predicate Logic there are two new logical connectives, the* Universal Quantifier* (∀x) and the *Existential Quantifier* (∃x). These are used for symbolizing certain English constructions (they also have their own rules of inference and their own semantics, which we will learn about later).

Logical System

2013

Some predicate logic proofs or derivations using Gentzen calculus. Try to prove them. Click on a line to select it. Select one or more lines, apply the appropriate rule off the Rules menu. (Click 'Derive It' off the Wizard Menu, if you want help).

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Topic

Logical System

2013

You may have derivations of your own that you wish to try. Just type, paste, or drag and drop, them into the panel, select your derivation, and click 'Start from selection'. [*Often copy-and-paste won't work directly from a Web Page; however, usually drag-and-drop will work!*]

You will need to use the correct logical symbols. Here they are

F ∴ F ∧ G ∼ ∧ ∨ ⊃ ≡ ∀ ∃ ∴ (or use the palette to produce them)