Wednesday, February 18, 2015

Is a dynamic geometry experiment a proof?

The following four topics can be approached in a number of interesting ways, including the use of dynamic geometry software (Geogebra, Geometers' Sketchpad, Cabri...)

Geogebra/ Geometers' Sketchpad circle geometry lesson 1: chords of a circle

Lesson 2: Angles in a circle

Lesson 3: Tangents

Lesson 4: Cyclic quadrilaterals

A link to Geogebra (a free shareware, open source dynamic geogebra app):

http://www.geogebra.org/cms/

The question: is a dynamic geometry experiment a proof? Is it convincing? valid? complete and watertight?

What would you say about a more traditional, deductive proof of the same theorems -- for example:

Proof of inscribed angle theorem

Proof that angles in the same segment of a circle are equal


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