List of interactive geometry software

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Template:Short description Interactive geometry software (IGS) or dynamic geometry environments (DGEs) are computer programs which allow one to create and then manipulate geometric constructions, primarily in plane geometry. In most IGS, one starts construction by putting a few points and using them to define new objects such as lines, circles or other points. After some construction is done, one can move the points one started with and see how the construction changes.

HistoryEdit

The earliest IGS was the Geometric Supposer, which was developed in the early 1980s.<ref>Template:Cite book</ref> This was soon followed by Cabri in 1986 and The Geometer's Sketchpad.

ComparisonEdit

There are three main types of computer environments for studying school geometry: supposersTemplate:Vague, dynamic geometry environments (DGEs) and Logo-based programs.<ref>Template:Cite book </ref> Most are DGEs: software that allows the user to manipulate ("drag") the geometric object into different shapes or positions. The main example of a supposer is the Geometric Supposer, which does not have draggable objects, but allows students to study pre-defined shapes. Nearly all of the following programs are DGEs. For a related, comparative physical example of these algorithms, see Lenart Sphere.

License and platformEdit

The following table provides a first comparison of the different software according to their license and platform.

Software Cost (USD) Licence Platforms
Cabri Geometry Template:Dunno Template:Proprietary Windows, macOS
C.a.R. Template:Free Template:Free Windows, Linux, macOS
CaRMetal Template:Free Template:Free Windows, Linux, macOS
Cinderella 1.4 Template:Free Template:Proprietary Windows, Linux, Mac OS X (Java)
Cinderella 2.0 Template:Free Template:Proprietary Windows, Linux, Mac OS X (Java)
DrGeo Template:Free Template:Free Windows, Linux, Mac OS X
GeoGebra Free/Paid citation CitationClass=web

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Windows, Linux, Mac OS X
Geom Template:Free Template:Dunno Windows, MacOS, Linux
The Geometer's Sketchpad 70.02 US$ Template:Proprietary Windows, Mac OS X (Java)
Geometry Expert (GEX) Template:Dunno Template:Dunno Windows, Linux, Mac OS X
GEUP Template:Dunno Template:Proprietary Windows
Kig Template:Free Template:Free Linux
KSEG Template:Free Template:Free Windows, Linux, Mac OS X
WIRIS Template:Dunno Template:Proprietary Linux, Windows, Mac OS X (Java)

3D SoftwareEdit

Software Cost (USD) Licence Platforms
Archimedes Geo3D Template:Depends Template:Proprietary Windows/Mac OS X/Linux
GeoGebra (from version 5.0 Beta) Free/Paid GeoGebra License<ref name="geogebra-license" /> Windows, Linux, Mac OS X, Android, iOS, Windows RT
GEUP 3D Template:Dunno Template:Proprietary Windows
Yenka 3D Shapes Template:Depends Template:Proprietary Windows
WIRIS Template:Dunno Template:Proprietary Windows, Linux, Mac OS X

General featuresEdit

The following table provides a more detailed comparison:

Software Calculations Macros Loci Animations Scripting Assignments LaTeX export Web export Multilingual Proofs Extra
Cabri II Plus Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes (with plug-in) Template:No Template:Yes Template:Yes Template:Yes (on relations) Available on TI Calculator
Calques 3D Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:No Template:No Template:Yes (FRA ENG DEU ESP PTG) Template:Yes (on relations) Experimental connection with some CAS
CaR Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:Dunno
CaRMetal Template:Yes (recursive) Template:Yes Template:Yes Template:Yes (multiple) Template:Yes (JavaScript) Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes (probabilistic) Amodality, folder system, the Monkey
Cinderella Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes (PDF) Template:Yes Template:Yes Probabilistic Several geometries, Physics simulations
Ganja.js Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:No Template:No 2D and 3D, projective and conformal, Geometric Algebra.
GCLC Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:Yes Readable proofs, support for 3D
GeoGebra Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes (JavaScript) Template:No Template:Yes (PSTricks & PGF/TikZ) Template:Yes Template:Yes (55 languages) Template:Yes CAS, HTML5 Export (from version 4.2)
3D & Automatic Proof (from version 5.0)
Geometria Template:Yes Template:No Template:Yes Template:Yes Template:No Template:Yes Template:No Template:Yes Template:Yes Template:No Two-role (teacher, student) model
Geometrix Template:Yes Template:No Template:Yes Template:Yes Template:No Template:Yes Template:No Template:No Template:Yes Template:Yes Interactive proof, diagram checking, teacher/student models, labels with dynamic placeholders
Geometry Expressions Template:Yes Template:No Template:Yes Template:Yes Template:No Template:No Template:Yes Template:Yes (Interactive HTML5/JS Apps) Template:Yes Template:No Symbolic calculations, which can be copied as input for CAS, TeX, and source code in 21 formats/languages. Functions. Arcs on any function or curve. Website for exported HTML5 Canvas and JavaScript Interactive Apps (Euclid's Muse).
GeoNext Template:Yes Template:No Template:No Template:Yes Template:Dunno Template:Dunno Template:No Template:Dunno Template:Yes Template:No Available as a web app
Géoplan-Géospace Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:Yes (activeX) Template:Yes Template:Yes Sequences, 2D & 3D, human readable file format
GeoProof Template:Yes Template:No Template:No Template:No Template:No Template:No Template:Yes Template:No Template:No Template:Yes Automatic formal proofs
GEUP Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:Dunno Template:No Template:Yes Template:No CAD functionality through CADGEUP
iGeom Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:Yes Template:No Template:Yes Template:Yes Probabilist Recurrent scripts
Kig Template:Yes Template:Yes Template:Yes Template:No Template:Yes (Python) Template:No Template:Yes (PSTricks) Template:No Template:Yes Template:No Labels with dynamic placeholders
Live Geometry Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:No Template:No Template:No Template:No Includes player.
Sarit2d Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:Yes Available on web
Sketchpad Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:Dunno Template:Yes (limited) Template:Yes Template:No Functions & function plots, symbolic differentiation, mathematical notation
Tabula Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:No Template:No Template:No Template:No Folding, cutting, taping, marker, and working instrument models.
Tabulae Template:Yes Template:Yes Template:Yes Template:No Template:No Template:No Template:No Template:Yes Template:Yes Template:No Collaborative sessions over the internet.
Cabri 3D Template:Yes Template:No Template:No Template:Yes Template:No Template:No Template:No Template:Yes (limited) Template:Yes Template:No Template:Dunno
Archimedes Geo3D Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:No Template:No Template:No (Eng De Fr) Template:No Intersection of Loci
GEUP 3D Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:No Template:Yes Template:No CAD functionality through CADGEUP
Netpad Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:No Template:Yes Template:No Template:Yes Base on Web
Software Calculations Macros Loci Animations Scripting Assignments LaTeX export Web export Multilingual Proofs Extra

MacrosEdit

Features related to macro constructions: (TODO)

Software Allows recursity Allows saving
Cabri II Plus Template:Yes Template:Yes
Calques 3D Template:No Template:Yes
GCLC Template:No Template:No
GeoGebra Template:Yes Template:Yes
Géoplan-Géospace Template:Yes Template:Yes
GEUP Template:Yes Template:Yes
iGeom Template:Yes Template:Yes
Kig Template:Dunno Template:Yes
KSEG Template:Yes Template:Yes
Sketchpad (GSP) Template:Yes (via Iteration) Template:Yes

LociEdit

Loci features related to IGS: (TODO)

Software Take a point of a locus Intersection of two loci
Cabri II Plus Template:Yes Template:Yes
Calques 3D Template:No Template:No
CaR Template:Yes Template:Yes
GeoGebra Template:Yes Template:No
Géoplan-Géospace Template:Yes Template:No
GEUP Template:Yes Template:Yes
iGeom Template:Yes Template:No
Kig Template:Yes Template:No
Sketchpad (GSP) Template:Yes Template:No
NetPad Template:Yes Template:Yes

ProofEdit

We detail here the proof related features. (TODO)

Software Interactive Proofs Automatic Proofs Probabilist Proofs
Cabri II Plus Feedback for Template:No Template:Yes in Cabri I
Cinderella Template:No Using external CAS Template:Yes
GCLC Template:No Template:Yes Template:No
GeoGebra Template:Yes Template:Yes Template:No
Geometrix Template:Yes Template:Yes Template:No
Géoplan-Géospace Template:No Template:No Template:Yes
GeoProof Template:Yes Template:Yes Template:No
iGeom Template:No Template:No Template:Yes
Jeometry Template:No Template:Yes Template:No
NetPad Template:Yes Template:Yes Template:Dunno

Measurements and calculationEdit

Measurement and calculation features related to IGS: (TODO)

Software Arbitrary Precision Arithmetic expressions Trigonometric functions If Object existence test
Cabri Template:Yes Template:Yes Template:Yes Template:Yes Template:No
Calques 3D Template:No Template:Yes Template:Yes Template:No Template:No
C.a.R. Template:No Template:Yes Template:Yes Template:Yes Template:Yes
GCLC Template:No Template:Yes Template:Yes Template:Yes Template:Yes
GeoGebra Template:No Template:Yes Template:Yes Template:Yes Template:Yes (JavaScript)
Geometria Template:No Template:Yes Template:Yes Template:No Template:No
Géoplan-Géospace Template:No Template:Yes Template:Yes Template:Yes (μ function) Template:No
GeoProof Template:Yes Template:Yes Template:Yes Template:Yes Template:No
Geometrix Template:No Template:Yes Template:Yes Template:Yes Template:No
iGeom Template:No Template:Yes Template:Yes Template:No Template:No
NetPad Template:Yes Template:Yes Template:Yes Template:Yes Template:No

Graphics export formatsEdit

Software PNG BMP TIFF GIF SWF SVG EMF Fig Postscript Pdf LaTeX/Eukleides LaTeX/Pstricks LaTeX/PGF/TikZ Asymptote
Calques 3D Template:No Template:No Template:No Template:No Template:No Template:No Template:No Template:Yes Template:No Template:No Template:No Template:No Template:No Template:No
C.a.R. Template:Yes Template:No Template:Dunno Template:Dunno Template:Dunno Template:Yes Template:No Template:Yes Template:Yes Template:No Template:No Template:Yes Template:Dunno Template:Dunno
Cinderella Template:Yes Template:Yes Template:Dunno Template:Dunno Template:Dunno Template:Dunno Template:Dunno Template:Dunno Template:No Template:Yes Template:Dunno Template:Dunno Template:Dunno Template:Dunno
GCLC Template:No Template:Yes Template:No Template:No Template:No Template:Yes Template:No Template:No Template:Yes Template:No Template:No Template:Yes Template:Yes Template:No
GeoGebra Template:Yes Template:No Template:No Template:Yes (animated) Template:No Template:Yes Template:Yes Template:No Template:Yes Template:Yes Template:No Template:Yes Template:Yes Template:Yes
Geometry Expressions Template:Yes Template:Yes Template:Yes Template:Yes (animated) Template:No Template:No Template:Yes Template:No Template:Yes Template:No Template:Dunno Template:Dunno Template:Dunno Template:Dunno
GeoProof Template:Yes Template:No Template:Dunno Template:Dunno Template:Dunno Template:Yes Template:No Template:No Template:No Template:No Template:Yes Template:No Template:Dunno Template:Dunno
Kig Template:Yes Template:Yes Template:Dunno Template:Dunno Template:Dunno Template:Yes Template:No Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:Dunno Template:Dunno
KmPlot Template:Yes Template:Yes Template:Dunno Template:Dunno Template:Dunno Template:Yes Template:Dunno Template:Dunno Template:Dunno Template:Dunno Template:Dunno Template:Dunno Template:Dunno Template:Dunno
KSEG Template:Yes Template:Yes Template:Dunno Template:Dunno Template:Dunno <math>\alpha</math> Template:No Template:No Template:Dunno Template:No Template:No Template:No Template:Dunno Template:Dunno
Geometrix Template:No Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:No Template:No Template:No Template:No Template:No Template:Dunno Template:Dunno
iGeom Template:No Template:No Template:No Template:Yes Template:No Template:No Template:No Template:No Template:Yes Template:No Template:No Template:No Template:Dunno Template:Dunno

Object attributesEdit

Software Color Filled/Not filled Width Transparency Shown/Hidden Layer Shape of points Type of line
Cabri Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:Yes
Calques 3D Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:Yes Template:Yes Template:Yes
C.a.R. Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes
GCLC Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:Yes Template:Yes Template:Yes
GeoGebra Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes
Geometria Template:Yes Template:Yes Template:No Template:Yes Template:Yes Template:Yes Template:No Template:Yes
Geometry Expressions Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No (but size) Template:Yes
Géoplan-Géospace Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:Yes
Kig Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:No Template:Yes Template:Yes
GeoProof Template:Yes Template:No Template:Yes Template:No Template:Yes Template:Yes Template:Yes Template:Yes
Geometrix Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:No Template:Yes Template:Yes
GEUP Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:Yes
iGeom Template:Yes Template:Yes Template:Yes Template:No Template:Yes Template:No Template:No Template:Yes
Sketchpad Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Dunno Template:Yes Template:Yes
NetPad Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:Yes Template:No (but size) Template:Yes

2D programsEdit

C.a.R.Edit

C.a.R. is a free GPL analog of The Geometer's Sketchpad (GSP), written in Java.

CabriEdit

Cabri Cabri was developed by the French school of mathematics education in Grenoble (Laborde, 1993)

CaRMetalEdit

CaRMetal is a free GPL software written in Java. Derived from C.a.R., it provides a different user interface.

CinderellaEdit

Cinderella, written in Java, is very different from The Geometer's Sketchpad. The later version Cinderella.2 also includes a physics simulation engine and a scripting language. Also, it nowTemplate:When supports macros, line segments, calculations, arbitrary functions, plots, etc. Full documentation is available online.

Dr GeniusEdit

Dr Genius was an attempt to merge Dr. Geo and the Genius calculator.

Dr. GeoEdit

Dr. Geo is a GPL interactive software intended for younger students (7-15). The later version, Dr. Geo II,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is a complete rewrite of Dr. Geo, for the Squeak/Smalltalk environment.

GCLCEdit

GCLC<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is a dynamic geometry tool for visualizing and teaching geometry, and for producing mathematical illustrations. In GCLC, figures are described rather than drawn. This approach stresses the fact that geometrical constructions are abstract, formal procedures and not figures. A concrete figure can be generated on the basis of the abstract description. There are several output formats, including LaTeX, LaTeX/PStricks, LaTeX/Tikz, SVG and PostScript. There is a built-in geometry theorem prover (based on the area method). GCLC is available for Windows and Linux. WinGCLC is a Windows version of GCLC with a graphical interface that provides a range of additional functionalities. GCLC is open source software (licence CC BY-ND).

GeoGebraEdit

GeoGebra is software that combines geometry, algebra and calculus for mathematics education in schools and universities. It is available free of charge for non-commercial users.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

  • License: open source under GPL license (free of charge)
  • Languages: 55
  • Geometry: points, lines, all conic sections, vectors, parametric curves, locus lines
  • Algebra: direct input of inequalities, implicit polynomials, linear and quadratic equations; calculations with numbers, points and vectors
  • Calculus: direct input of functions (including piecewise-defined); intersections and roots of functions; symbolic derivatives and integrals (built-in CAS); sliders as parameters
  • Parametric Graphs: Yes
  • Implicit Polynomials: Yes
  • Web Export: all constructions exportable as web pages as a Java applet
  • Macros: usable both as tools with the mouse and as commands in the input field
  • Animation: Yes
  • Spreadsheet: Yes, the cells can contain any GeoGebra object (numbers, points, functions etc.)
  • Dynamic text: Yes (including LaTeX)
  • Platforms: Mac OS, Unix/Linux, Windows (any platform that supports Java 1.5 or later)
  • Continuity: uses a heuristic 'near-to-approach' to avoid jumping objects

GeoKone.NETEdit

GeoKone.NET<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is an interactive recursive natural geometry (or "sacred geometry") generator that runs in a web browser. GeoKone allows the user to create geometric figures using naturalistic rules of recursive copying, such as the Golden ratio.

GeologEdit

Geolog<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is a logic programming language for finitary geometric logic.

Geometry ExpressionsEdit

Geometry Expressions<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Does symbolic geometry. It uses real symbolic inputs and returns real and symbolic outputs. It emphasises use with a Computer Algebra System (CAS), as well as exporting and sharing via interactive HTML5, Lua and OS X dashboard widget apps.

The Geometer's SketchpadEdit

The Geometer's Sketchpad (GSP)

  • Deterministic
  • Languages: English, Spanish, Danish, Russian, Korean, Thai, Traditional and Simplified Chinese, French, Lithuanian (current version); others (older versions)
  • Macros: Yes ("custom tools" and "scripts")
  • Java-applet: Yes
  • Animation: Yes
  • Locus: Yes, including point on locus
  • Assignments: No
  • Measurement/Calculations: Yes
  • Platform: Windows, Mac OS, TI-92+, works under Wine
  • Proofs: No

The Geometric SupposerEdit

Template:Expand section The Geometric Supposer<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Géoplan-GéospaceEdit

Template:Expand section

GeonextEdit

Geonext was developed by the University of Bayreuth until 2007 and is completely implemented in Java. Its final version was 1.74.

GeoProofEdit

GeoProof<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is a free GPL dynamic geometry software, written in OCaml.

GEUPEdit

GEUP is a more calculus-oriented analog of The Geometer's Sketchpad.

  • Deterministic
  • Languages: English, French, German, Italian, Portuguese, Spanish
  • Macros: Yes
  • Java-applet: No
  • Animation: Yes
  • Locus: Yes, including point on locus
  • Assignments: No
  • Measurement/Calculations: Yes
  • Platform: Windows
  • Proofs: No

GRACEEdit

GRACE (The Graphical Ruler And Compass Editor) is an analog of The Geometer's Sketchpad (GSP), written in Java.

JeometryEdit

Jeometry is a dynamic geometry applet.

KigEdit

Kig is a free (GPL) analog of The Geometer's Sketchpad (GSP) for KDE, but more calculus-oriented. It is a part of the KDE Edutainment Project.

KmPlotEdit

KmPlot is a mathematical function plotter released under the free GPL license. Includes a powerful parser and precision printing in correct scale. Simultaneously plot multiple functions and combine function terms to build new functions. Supports functions with parameters and functions in polar coordinates. Several grid modes are available. Features include:

  • powerful mathematical parser
  • precise metric printing
  • different plot types (functions, parametric, polar)
  • highly configurable visual settings (plot line, axes, grid)
  • export to bitmap format (BMP and PNG) and to Scalable Vector Graphics (SVG)
  • save/load complete session in readable XML format
  • trace mode: cross-hair following plot, coordinates shown in the status bar
  • zooming support
  • ability to draw the 1st and 2nd derivative and the integral of a plot function
  • support user-defined constants and parameter values
  • various tools for plot functions: find minimum/maximum point, get y-value and draw the area between the function and the y-axis

KSEGEdit

KSEG is a free (GPL) analog of The Geometer's Sketchpad (GSP) with some unique features. This software can handle heavy, complex constructions in Euclidean geometry.

  • Deterministic
  • Languages: Dutch, English, French, Chinese, German, Hungarian, Italian, Japanese, Norwegian Bokmål, Portuguese, Russian, Spanish, Turkish, Welsh
  • Macros: Yes. Editable and with support for recursion
  • Java-applet: No
  • Animation: No
  • Locus: Yes, but no direct way to place a point on a locus.
  • Assignments: No
  • Measurement/Calculations: Yes (the calculator is a bit strange)
  • Platform: Unix/Linux, Windows, Mac OS (any platform that supports Qt)
  • Proofs: No
  • Extra: Editable

Live GeometryEdit

Live Geometry is a free CodePlex project that lets you create interactive ruler and compass constructions and experiment with them. It is written in Silverlight 4 and C# 4.0 (Visual Studio 2010). The core engine is a flexible and extensible framework that allows easy addition of new figure types and features. The project has two front-ends: WPF and Silverlight, which both share the common DynamicGeometry library.

TracenPocheEdit

TracenPoche is a completely Adobe Flash program. It is available in English, Spanish, and French.

3D programsEdit

Template:Expand section

Cabri 3DEdit

Cabri Geometry

Archimedes Geo3DEdit

Archimedes Geo3D is a shareware program designed for 3D geometric constructions. It extends traditional ruler and compass constructions into 3D space, allowing users to work with elements such as points, lines, circles, planes, spheres, vectors, and loci. This software is compatible with Windows, macOS, and Linux platforms.

Euler 3DEdit

Euler (software)

Euler 3D is a program that allows you to create and manipulate your own polyhedrons. It has a number of facilities: transformations, animations, creating duals, import/export VRML, etc.

Free registration required.

GeoGebraEdit

GeoGebra, includes a 3D mode since version 5.0

GeomviewEdit

Geomview

GEUP 3DEdit

GEUP

Continuity versus determinismEdit

All these programs can be divided into two category: deterministic and continuous. GeoGebra can be deterministic or continuous (one can change it in preferences).

All constructions in the deterministic programs (GSP, Cabri, Kseg and most of others) are completely determined by the given points but the result of some constructions can jump or behave unexpectedly when a given point is moved.

On the contrary, some constructions in continuous programs (so far only Cinderella and GeoGebra), depend on the number of hidden parameters and in such a way that moving a given point produces a continuous motion of the construction, as a result, if the point is moved back to the original position the result of construction might be different.

Here is a test to check whether a particular program is continuous:

Construct the orthocenter of triangle and three midpoints (say A', B' C' ) between vertices and orthocenter.

Construct a circumcircle of A'B'C' .

This is the nine-point circle, it intersects each side of the original triangle at two points: the base of altitude and midpoint. Construct an intersection of one side with the circle at midpoint now move opposite vertex of the original triangle, if the constructed point does not move when base of altitude moves through it that probably means that your program is continuous.

Although it is possible to make a deterministic program which behaves continuously in this and similar simple examples, in general it can be proved that no program can be continuous and deterministic at the same time.<ref>Kortenkamp, Ulrich (1999): Foundations of Dynamic Geometry, Dissertation, ETH Zurich 1999. Available online at http://kortenkamps.net/papers/1999/diss.pdf</ref>

See alsoEdit

ReferencesEdit

Template:Reflist

External linksEdit