Jonathan Odom
Educational Technology
Lesson Plan Title: Studying Interior Angles of Triangles
Concept/Topic to Teach: Interior Angle Measures of Triangles
Standards Addressed: Alabama High School Geometry Standard #4: Determine
the interior measure of angles associated with polygons.
Specific Objectives: Students will be able to calculate the sum of the interior
angles and manipulate the shape so that the total will always be 180 degrees.
Required Materials: Pearson Common Core Geometry, Geometer’s Sketchpad
Computer Program on Student Computers, Interwrite Board, projector,
Mobi, Paper, Pencil, Scissors, website
http://www.mathopenref.com/triangleinternalangles.html
Anticipatory Set (Lead-In): Allow students to use paper, pencil, and scissors to try
and construct a straight angle from a previously drawn triangle.
Step-By-Step Procedures for Teaching the Lesson: The teacher will provide the
procedures.
 Explain directions for opening activity.
 Explain directions for geometer’s sketchpad.
 The teacher will construct a triangle using geometer’s sketchpad.
 The teacher will demonstrate how interior angle measures
change, but the sum of the angles remains the same.
 The teacher will instruct the students to construct a triangle on
their computer.
 Students will be able to move corners of triangles to see that
angle measurements change, but the sum of the measures remain
the same.
 Students will also be able to see how the exterior angles of the
triangle change as the interior angles change.
 The teacher will show the students the website
http://www.mathopenref.com/triangleinternalangles.html.
 The students will be instructed to follow that link if they need
extra demonstrations.
 Students will then be given practice problems to work. The
problems will consist of missing angle measurements. They will
have to solve for these missing measurements.
Guided Practice/Monitoring: The teacher will model how to construct a triangle
and how to check angle measurements using Geometer’s Sketchpad.
Students will be instructed to construct there own triangle using
geometer’s sketchpad and their computer. While they are working, the
teacher will monitor their progress and provide input to students that
need help. Students will then be given a series of triangles with missing
angles. Using geometer’s sketchpad, they will solve for the missing
angles. The teacher will monitor their progress and check for
understanding.
Closure (Reflect Anticipatory Set): The teacher will construct a straight angle
using the interior angles of triangle using geometer’s sketchpad. This
will show students why the angles have a sum of 180 degrees.
Assessment Based on Objectives: Students will be able to with 80% accuracy
calculate the sum of the interior angles and manipulate the shape so
that the total will always be 180 degrees. Students will be assessed on
their understanding of this objective.
Adaptations (For Students with Special Needs): One student struggles with basic
typing skills. For this student, we have a “talk to type” application that
he can use. This will allow him to quietly talk into a microphone which
helps him navigate through the program. Also, all students with
learning disabilities will be given extra attention and any other
accommodation that is stated in their IEP.
Extensions (For Advanced Students): Advanced students will be asked to write a
brief description of what would happen if the angle measurements were
less than 180o or greater than 180o. What is the shape formed? Is it still
a triangle? Why or why not?
Possible Connections to Other Subjects: Students will practice construction,
which is a part of physics. Students will also be asked to write about their
findings, which is a part of English/Reading.
Reflection: This was one of the best lessons that I have conducted. Students were
actively engaged. They really seemed to love working with the
constructions. They also liked be able to visualize what was
happening with the angles. When I do this again, I plan to provide
more time. For some students, it took them a little while to get
accustomed to the program. I could also start with an easier
assignment to teach students to use the program. Overall, the lesson
was a great success and students really responded well to it.