derivations

12/22/05

Introduction to Tactics

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

Or Introduction

Rules for the Copi System

1/8/26 under construction

12/28/20

Roll your own derivations

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 ∼ ∧ ∨ ⊃ ≡ ∀ ∃ ∴

Tutorial 6: Abelian Groups Tutorial 7: Boolean Algebra Tutorial 8: Linearly Ordered Sets Coming sometime!

1/2/2021

Solutions

Theorem 1

Theorem 2

1/17/20

1/17/20

12/23/20

Tutorial 5: Number Theory II

Formal Number Theory. Just more theorems for you.

Recall

Formal Number Theory has five proper symbols {=,',+, .,0} and six proper axioms

(∀x)(∀y)(x'=y'⊃x=y),
(∀x)~(x'=0),
(∀x)(x+0=x),
(∀x)(∀y)(x+y'=(x+y)'),
(∀x)(x.0=0),
(∀x)(∀y)(x.y'=x.y+x)

And the axiom (metalanguage) schema of induction. If φ[n] is any formula in the object language with free variable n then

(φ[0]∧(∀n)(φ[n]⊃φ[n'])) ⊃ (∀n)φ[n]

12/23/20