Download Identify, Measure, and Construct Angles and Triangles in a highly

Identify, Measure, and Construct Angles and Triangles in a highly engaging lesson
using the concept of the Bermuda Triangle” as the foundation for engagement
State Common Core Objectives for 4th grade: Recognize angles as geometric shapes
that are formed wherever two rays share a common endpoint, and understand concepts of
angle measurement. Draw and identify lines and angles, and classify shapes by
properties of their lines and angles.
Activity: Students will learn to measure, identify, and construct equilateral, isosceles,
and scalene triangles while learning about the mysteries of the Bermuda Triangle, and
creating a mysterious triangle of their own.
Materials:
• Classroom world map or globe
• Pencil
• Lined paper if you have students write their 3-sentence mysteries vs. oral telling
only
• A Protractor for each student
• Copies of a world map for each student (a free downloadable continent version of
the world is available at http://www.eduplace.com/ss/maps/world.html )
• A brief history of the Bermuda Triangle found at
http://www.pbs.org/wnet/savageseas/captain-side-bermuda.html
Engagement: Ask student if they have ever heard of the Bermuda Triangle, and allow
time for the students to share their responses. Then, using the classroom world map or
globe, locate the Bermuda Triangle for the students. Follow-up by read “The Devil’s
Triangle?” aloud to the students. (Found at the pbs website indicated above in
materials.)
Procedure:
You can make this lesson whatever you want, in terms of defining and working with as
many or as few concepts as is your objective regarding triangles, angles, and
measurement. The following website has all the definitions you’ll need, no matter how
far you take the lesson. http://www.1728.org/triang.htm
Provide each student with a world map
Have students locate and draw the Bermuda Triangle on their maps by helping them to
identify and draw three points, which they then connect with lines to create a (Bermuda)
triangle by using the straight edge of their protractors.
Have students measure the length of each side of their Bermuda Triangles in cm. and
write their measurements along each line.
Model measuring the angles with a protractor. For this lesson, modeling measuring an
angle with a protractor should be a review of lessons that have come before. If this is not
true, allow lots of time to model and practice measuring angles at this point and continue
on to the rest of this lesson in the next class period.
Draw and define examples of equilateral, Isosceles, and scalene triangles on the board or
overhead.
Model the construction of another “mysterious triangle” on the world map by marking 3
points on the map and connecting the points to make a triangle. Name your triangle and
give it a made-up mystery, for instance: The “Duck Duck Goose Triangle” is known as a
place where birds fly in, but they don’t fly out. A plane load of people once saw a group
of migrating ducks, flying along side them, suddenly disappear in mid-air. Birds with
attached tracking devices have disappeared when flying through the triangle. No people,
planes, ships, or fish jumping out of the water in the Duck Duck Goose Triangle have
ever disappeared, only birds.
Measure the sides and angles of your new mysterious triangle and identify the type of
triangle by sides and angles.
Guided Practice:
Have Students construct their own mysterious triangles on their maps.
Have each student measure its angles and length of its sides, labeling the triangle with
these measurements.
Have each student identify what type of triangle his mysterious triangle is, and label the
triangle on his map.
On a piece of lined paper, have each student name his triangle and write a summary of
the mystery surrounding his triangle (3 or 4 sentences)
Independent Practice:
Have students construct two more triangles independently.
Have students measure the angles of their triangles and the length of its sides.
Have each student share the geometric descriptions of his triangle with the class, as well
as a 3 or 4 sentence summary of the mystery surrounding his triangle.
Assessment: In-class work.
Closure: In addition to having students share their triangles and mysteries, have students
share one thing new they have learned about angles and triangles, and their relationship
to each other.
Extension: Have students construct a right “mysterious triangle” using a protractor and
ruler. Have students measure the other two angles of their right Isosceles triangle.
Discuss. You draw another right Isosceles triangle on the board and measure the angles.
Have the students draw yet another right Isosceles triangle and measure the angles.
Compare and discuss the outcome.
This lesson is very effective. The students love constructing their own “mysterious
triangles” in order to concoct their mysteries. This lesson usually becomes a lesson of
not only geometry, but also of folklore, geography, and culture. One student from South
Africa located another “mysterious triangle” on the map that she identified as a part of
South African folklore, and share the story. The students readily connect triangle/angle
concepts and relationships as they identified their mysterious triangles.