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Functions can not be seen. Rainer Kaenders University of Cologne GeoGebra Conference Linz 2011. Functions can not be seen. … but can be represented GeoGebra can make the identification of functions with their graphs stronger
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Functionscan not beseen Rainer Kaenders University of Cologne GeoGebra Conference Linz 2011
Functionscan not beseen • … but canberepresented • GeoGebra canmaketheidentificationoffunctionswiththeirgraphsstronger • Many different representations: showthatthereis not therepresentationof a function • Eachrepresentationhas ist ownpossibilitiesandfailures. • GeoGebra ascatalystformathematics!
Examples Van Dormolen[Dor78], Malle (z.B. in [Mal93], S. 265 oder [Mal00], Spivak ([Spi67], S. 79, www.dynagraph.de Hans-Jürgen Elschenbroich
Composition • IdenticalFunctionhas a naturalappearance • The increase / decreasefrom x to f(x) becomesvisible • Inverse function easy toconstruct • Involutions, f(x) with f f = id, • Projections, p(x) with p p = p • CompositionandDecompositionoftwofunctions • Iterationscanbevisualized • General notions on mappingsofsets (injective, surjective, sections, …)
Deltoide and
Run alongthe Edge Howtouselevelcurvestorepresentfunctions?
r() = C a
Outline • Functionscan not beseen • Nomogrammes - Composition - Linear Functions - Linear Approximation - Translation of Domain and Value Line - SolvingEquations • Run alongthe Edge - TobleroneDiagram - ProductandSumofFunctions • Outlook - VariousCoordinates