Investigating Parallel Lines
Name:
and a Transverse. Go to the Tab- “Parallel Lines and a transversal” in Parallellines.gsp
Aim: To use Geometer’s Sketchpad to investigate corresponding and alternate angles.
F
B
G
A
Measuring the Angles.
H
D
C
1. Select the Arrow tool
and make sure nothing is highlighted in your sketch.
E
2. To measure the angle  ABC select the points A, B and then C, IN THAT ORDER! and select
Angle in the Measure menu.
Observation
1. Using the instructions above, measure the angles FGB and GHD.
corresponding angles. How do their measurements compare?
They are a pair of
2. For each angle given below, list its corresponding angle and explain how the measures compare.
Measure the angles if you need to.
a) FGA
b) HGA
c) BGH
3. Drag point E slowly and notice the measures of each pair of corresponding angles. How do
their measures compare?
Complete the following statement: If two parallel lines are cut by a transversal, then the
corresponding angles are
4. Using the instructions above, measure the angles HGA and GHD. They are a pair of
alternate angles, sometimes known as “Z” angles. How do their measurements compare?
5. Find the other pair of alternate angles.
6. Drag point E slowly and notice the measures of each pair of alternate angles. How do their
measures compare?
Complete the following statement: If two parallel lines are cut by a transversal, then the
alternate angles are
7. On the diagram below mark the 4 pairs of corresponding angles with the numbers 1-4 and the
2 pairs of alternate angles with the numbers 5 and 6. The first one has been done for you.
F
G
1
B
A
1
H
D
C
E