CONSTRUCTIONS

Objective: Use a compass and straight edge to construct congruent segments and angles. Introduction to Constructions

Constructions: The drawing of various shapes using only a pair of compasses and straightedge or ruler. No measurement of lengths or angles is allowed.

** You are not allowed to measure angles with a protractor, or measure lengths with a ruler. Compasses

Compasses are a drawing instrument used for drawing circles and arcs. It has two legs, one with a point and the other with a pencil or lead. You can adjust the distance between the point and the pencil and that setting will remain until you change it.

Try drawing some circles and arcs on your paper. Straightedge

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 0° 0 1 2 3 4 5

A straightedge is simply a guide for the pencil when drawing straight lines. In most cases you will use a ruler for this, since it is the most likely to be available, but you must not use the markings on the ruler during constructions. Why we learn about constructions

The Greeks formulated much of what we think of as geometry over 2000 years ago. In particular, the mathematician Euclid documented it in his book titled "Elements", which is still regarded as an authoritative geometry reference. In that work, he uses these construction techniques extensively, and so they have become a part of the geometry field of study. They also provide insight into geometric concepts and give us tools to draw things when direct measurement is not appropriate. Copying a line segment or Constructing Congruent Segments

http://www.mathopenref.com/constcopysegment.html Copying a line segment or Constructing Congruent Segments Construct a copy of AB. Name your segment YZ. Construct a copy of BC from the triangle. The congruent segment should have one endpoint at P. Name it PR.

A P

B C Sum of line segments

http://www.mathopenref.com/constaddsegments.html Sum of line segments

Construct a line segment whose length is equal to the sum of the given line segments.

a b

c Construct a segment whose length is two times longer than the given segment. Construct a line segment whose length is equal to the perimeter of the triangle below.

Label the segment AB Copying an Angle or Constructing Congruent Angles

http://www.mathopenref.com/constcopyangle.html Copying an Angle or Constructing Congruent Angles

Construct an angle congruent to each of the angles below.

Z N M X

P

Y