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Discussion: All Tools in Geometry on Computer
Topic: geom construction software with compass -> arcs, not circles


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Subject:   RE: geom construction software with compass -> arcs, not circles
Author: Dr. Fred
Date: Sep 23 2011
The Geometry Toolkit from Ventura Educational Systems has a simulation of basic
construction tools, a compass and straight edge. The software allows you to set
the size of the arc and position.  The radius is determined by the first arc and
subsequent arcs have the same radii which simulates the process of picking up a
compass and moving it to a new point without changing the size of the arc.  This
is useful in many basic constructions.  Most of the commonly taught
constructions can be done such as bisecting a line segment or angle.  Creative
constructions can also be done using the 'paint bucket fill tool' to color a
constructed design, for example an inscribed hexagon with diagonals.


On Sep 22 2011, jdad wrote:
> My son is taking geometry and has physical difficulty writing (he
> has a tremor), so doing compass and straight edge constructions is
> very frustrating for him even though he understands the principles.
> I've been trying to find some software for him to use, so he can
> create neat, accurate work with less frustration.

I've purchase
> geometer's sketchpad, tried the Cabri demo, GeoGebra, Live Geometry,
> Cinderella, and numerous others but I've consistently run into the
> same problem.  When you use the compass, it creates a full circle.
> If I'm doing a construction like an inscribed octagon, the screen is
> littered with circles, whereas the way you'd do it by hands just
> leaves the arc for the angle bisections and perpendicular bisector.
> My son balks at all the ink and doesn't want his work to be
> different than the other kids.  Plus, it's hard to even find the
> intersections among the maze of lines.

I've tried creating a
> custom tool in geometer's sketchpad by using the compass and
> creating an arc on a circle and hiding the circle.  How to I create
> another arc with the same radius though if I'm doing a perpendicular
> bisector?  Copy and paste?  Then I can't seem to "flip" the arc and
> anchor it to the point at the other end of the line segment.

The
> only thing I've found that draws arcs is this old, klunky java
> applet from 1997.
> http://strader.cehd.tamu.edu/geometry/bisectangle1.0/bisectangle.html
> Is there any full-featured geometry software (i.e., he can print,
> save, etc.) with this sort of compass implementation?  I guess what
> I want is "arc by radius" (a la "circle by radius").  I see tools
> for drawing arcs through 3 points, on a circle, and by center and
> two points, but not by center and radius (and two points -- not
> necessarily on arc, but to give angle) as you'd use a physical
> compass.

Any other software to try or features I'm missing in
> sketchpad, geogebra, and company?

Thanks,
jdad

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