Copying Segments and Angles
Copying Segments and AnglesAdapted from Walch Education
Key ConceptsA geometric figure precisely created using only a
straightedge and compass is called a construction. A straightedge
can be used with patty paper (tracing paper) or a reflecting device
to create precise representations. Constructions are different from
drawings or sketches. A drawing is a precise representation of a
figure, created with measurement tools such as a protractor and a
ruler.1.2.1: Copying Segments and Angles2
Concepts, continuedA sketch is a quickly done representation of
a figure or a rough approximation of a figure.When constructing
figures, it is very important not to erase your markings. Markings
show that your figure was constructed and not measured and drawn.
An endpoint is either of two points that mark the ends of a line,
or the point that marks the end of a ray.
1.2.1: Copying Segments and Angles3Concepts, continuedA line
segment is a part of a line that is noted by two endpoints.An angle
is formed when two rays or line segments share a common endpoint. A
constructed figure and the original figure are congruent; they have
the same shape, size, or angle. Follow the steps outlined on the
next few slides to copy a segment and an angle.1.2.1: Copying
Segments and Angles41.2.1: Copying Segments and Angles5Copying a
Segment Using a CompassTo copy , first make an endpoint on your
paper. Label the endpoint C.Put the sharp point of your compass on
endpoint A. Open the compass until the pencil end touches endpoint
B. Without changing your compass setting, put the sharp point of
your compass on endpoint C. Make a large arc. Use your straightedge
to connect endpoint C to any point on your arc. Label the point of
intersection of the arc and your segment D.Do not erase any of your
markings. is congruent to .
1.2.1: Copying Segments and Angles6Copying a Segment Using Patty
PaperTo copy , place your sheet of patty paper over the segment.
Mark the endpoints of the segment on the patty paper. Label the
endpoints C and D. Use your straightedge to connect points C and D.
is congruent to .
1.2.1: Copying Segments and Angles7Copying an Angle Using a
CompassTo copy A, first make a point to represent the vertex A on
your paper. Label the vertex E.From point E, draw a ray of any
length. This will be one side of the constructed angle. Put the
sharp point of the compass on vertex A of the original angle. Set
the compass to any width that will cross both sides of the original
angle. Draw an arc across both sides of A. Label where the arc
intersects the angle as points B and C.(continued)1.2.1: Copying
Segments and Angles8Without changing the compass setting, put the
sharp point of the compass on point E. Draw a large arc that
intersects the ray. Label the point of intersection as F.Put the
sharp point of the compass on point B of the original angle and set
the width of the compass so it touches point C.Without changing the
compass setting, put the sharp point of the compass on point F and
make an arc that intersects the arc in step 5. Label the point of
intersection as D.Draw a ray from point E to point D.Do not erase
any of your markings.A is congruent to E. 1.2.1: Copying Segments
and Angles9Copying an Angle Using Patty PaperTo copy A, place your
sheet of patty paper over the angle.Mark the vertex of the angle.
Label the vertex E.Use your straightedge to trace each side of A.A
is congruent to E. Thanks for Watching!Ms. Dambreville
