# Construct 1: Compass and Straightedge with GeoGebra

Basic Constructions: Using only a pencil, a compass. and a straightedge (an unmarked ruler)

Regulation: You can "use" a ruler for a straightedge, but you cannot use the measurements on it!

What is a pencil, a compass. and a straightedge in GeoGebra?

Worksheet Materials (Handout & Teacher Page)

Pencil tools: Point and Intersection point
Staightedge tool: Line through two points and (if desired) Ray and Segment .
Compass tools: Circle with center and radius and the function Distance[]
Some fun tools for checking our work ... Angle and Distance

Materials for Offline Use

Zip for offline use: tri_median_right.zip (includes handout, teachers page, 2 ggb interactivities).
Requires freeware GeoGebra and sunJava player.

 Brief User uses GeoGebra to do pencil, straightedge and compass geometric constructions. Goal Understanding straightedge and compass constructions Grade 7-9 (7th grade, geometry) Strand Measurement and Geometry, Geometry Standards CA 7.MG.3.1,  CA Geometry 16.0 Keywords geometric, construct, construction, straightedge, compass, ruler, geogebra Comments Suitable for 7th-grade on up. Source Linda Fahlberg-Stojanovska (no copyright) Cost Activity and software is free to use Download Zip for offline use: tri_median_right.zip (includes handout, teachers page, 2 ggb interactivities) Requires freeware GeoGebra for offline use. Type Java Applet so requires free sunJava player

1. copy a line segment

Start: You start with a line segment \overline{AB} \,\,and a line m \,\,with a point C \,\,on it.

Goal: To construct a point D on m \,\,such that \overline{CD}\,\, is congruent to \overline{AB} \,\, (lengths of segments are equal).

2. copy an angle

2. copy an angle

3. bisect a line segment

3. bisect a line segment

4. bisect an angle

bisect an angle

5. construct a perpendicular (normal)

Start: You start with a  line m \,\,with a point A \,\,on m \,\,.
Goal: To construct (find) a line n passing through A \,\,and perpendicular (normal) to m \,\,.

6.construct parallel lines

Start: You start with a  line m \,\,with a point C \,\, NOT on m \,\,.
Goal: To construct (find) a line p passing through C \,\,and parallel to m \,\,.

Second Level Constructions: using a pencil, a compass and 2 triangles (similar, right, "unmarked").
Regulation: Probably best to use 2 30°-60°-90° triangles - easier to get closer parallel lines. (Remember you cannot use the measurements on the triangles!)

Here - in order to keep the user from getting bogged down in basic constructions, a user is allowed

• given a point A on a line m - to use his right triangle to draw a line n normal (perpendicular) to m through A and
• give a line m and a point C not on m - to use both triangles to draw a line p parallel to m through A.

These are 5 and 6 of Basic Constructions

Related themes:

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geometric, construct, construction, straightedge, compass, ruler, geogebra, application, geometry, program