Difference between revisions of "LocusEquation Command"
From GeoGebra Manual
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*If the locus is the whole plane then the implicit curve is the equation 0=0. | *If the locus is the whole plane then the implicit curve is the equation 0=0. | ||
*The calculation is done using [[w:Gröbner_basis|Gröbner bases]], so sometimes extra branches of the curve will appear that were not in the original locus. | *The calculation is done using [[w:Gröbner_basis|Gröbner bases]], so sometimes extra branches of the curve will appear that were not in the original locus. | ||
− | *Further informations and examples on [ | + | *Further informations and examples on [https://www.geogebra.org/m/KZVzqVEM geogebra.org]. A [https://www.geogebra.org/m/mbXQuvUV collection of implicit locus examples] is also available. |
*See also [[Locus Command|Locus]] command and [https://github.com/kovzol/gg-art-doc/tree/master/pdf/english.pdf GeoGebra Automated Reasoning Tools: A Tutorial].</div>}} | *See also [[Locus Command|Locus]] command and [https://github.com/kovzol/gg-art-doc/tree/master/pdf/english.pdf GeoGebra Automated Reasoning Tools: A Tutorial].</div>}} |
Latest revision as of 09:41, 18 September 2019
- LocusEquation( <Locus> )
- Calculates the equation of a Locus and plots this as an Implicit Curve.
- LocusEquation( <Point Creating Locus Line Q>, <Point P> )
- Calculates the equation of a Locus by using inputs tracer point Q and mover point P, and plots this as an Implicit Curve.
- Example:Let us construct a parabola as a locus: Create free Points A and B, and Line d lying through them (this will be the directrix of the parabola). Create free point F for the focus. Now create P on Line d (the mover point), then create line p as a perpendicular line to d through P. Also create line b as perpendicular bisector of Line Segment FP. Finally, point Q (the point creating locus line) is to be created as intersection of Lines p and b. Now
LocusEquation(Q,P)
will find and plot the exact equation of the locus.
- LocusEquation( <Boolean Expression>, <Free Point> )
- Calculates the locus of the free point such that the boolean condition is satisified.
- Example:
LocusEquation(AreCollinear(A, B, C), A)
for free points A, B, C calculates the set of positions of A that make A, B and C collinear—i.e. a line through B and C.
Notes:
- The Locus must be made from a Point (not from a Slider)
- Works only for a restricted set of geometric loci, i.e. using points, lines, circles, conics. (Rays and line segments will be treated as (infinite) lines.)
- If the locus is too complicated then it will return 'undefined'.
- If there is no locus then the implicit curve is the empty set 0=1.
- If the locus is the whole plane then the implicit curve is the equation 0=0.
- The calculation is done using Gröbner bases, so sometimes extra branches of the curve will appear that were not in the original locus.
- Further informations and examples on geogebra.org. A collection of implicit locus examples is also available.
- See also Locus command and GeoGebra Automated Reasoning Tools: A Tutorial.