# Construction in Geometry

## Presentation on theme: "Construction in Geometry"— Presentation transcript:

Construction in Geometry
We will be using a compass, Rulers and straightedges to copy lines angles construct angles. Steps and Diagrams from

Standards in this Chapter:
G.2.C. Explain and perform basic compass and straightedge constructions related to parallel and perpendicular lines G.2.A. Know, prove, and apply theorems about parallel and perpendicular lines. G.3.A. Know, explain, and apply basic postulated and theorems about triangles and the special lines, line segments, and rays associated with a triangle.

Pencil  Compass Point
Ruler: a tool with measurement markings to make straight lines Straightedge: a tool that has a straight side & no measurements (used for making straight lines) Compass: a tool that is used for making circles and arcs. They have a point and a pencil. Pencil  Compass Point

Sketch: A rough picture
Draw: Using tools with measurements (such as rulers) Construct: Straightedge & Compass

Copy a Line Segment Pick a point not on line segment PQ. Label it R.
Put the point of the compass on one of the endpoints of the line segment Open the compass until the pencil is on the other endpoint

4. Keeping the same measure. Move the compass point R and make an arc.

5. Pick a point on the arc and label it.
6. Use a straightedge and connect the two new points.

How to Copy an Angle: Draw a ray
Put the point of the compass on the vertex of the angle and make an arc. (mark the intersection pts)

3. Transfer the compass to the endpoint of the ray and make another arc at that same distance (don’t move the compass) and label the intersection point. 4. Then place the compass point on one of the intersection point of the original angle and extend it to the other intersection point (make an arc) M

5. Transfer the compass (keeping the same measure) to the intersection point on the ray and make an arc. 6. Label the intersection of the two arcs on the new ray. Connect the endpoint of the ray and the new intersection point.

Draw a Perpendicular Line (Bisecting a Line)
1. Place the compass pt on the endpoint and extend the compass pass the center of the line. 2. Make an arc on both sides of the line.

3. Keeping the same measure, transfer the compass to the other endpoint mark the arc on both sides of the line segment. 4. Connect the two intersection points of the arcs with a line