Total Duration: 
31 to 60 Minutes 
Materials and Resources: 
Pencils Three colored pencils or crayons Notebook paper Calculator Attached documentExterior Angle with Answers worksheet (make enough copies for all students) Website to make more worksheets: http://www.mathaids.com/Geometry/Triangle/Triangle_Exterior_Angle_Theorem.html One sheet of copy paper for all students Scissors 
Technology Resources Needed: 
https://www.youtube.com/watch?v=bBt6IPkZd8 The teacher will need to make his/her own worksheets. Just click on the link below and follow the steps on the page. http://www.mathaids.com/Geometry/Triangle/Triangle_Exterior_Angle_Theorem.html Desktop Computer/Interactive whiteboard Students will need a calculator. 
Background/Preparation: 
The teacher will need to preview the websites. The teacher will need to have colored pencils or crayons, scissors, and rulers for students to use. The teacher will need to know the ways to prove the sum of angles in a triangle. The teacher will need to know the culture of the class to keep students engaged during the group project. The teacher will need to know which students are the best peertutors. The teacher will click on the link to make original worksheets on Math Aids (http://www.mathaids.com/Geometry/Triangle/Triangle_Exterior_Angle_Theorem.html). The student will need to know that a line is 180 degrees. The student will need to know how to write and solve multistep equations. The student will need to know the terms exterior and remote interior angles. 
Before: 1. As the students enter the room, the teacher will have the bell ringer displayed on the interactive whiteboard, “How can you prove that a triangle has 180 degrees?” 2. After a couple of minutes, the teacher will ask some of the students to respond to the question. 3. The teacher will poll the class to see how many students agree with the given suggestions. During: 4. The teacher will ask the students to get into groups of three. 5. The teacher will give students a sheet of copy paper. Each group will receive a pair of scissors and three colored pencils or crayons. 6. With a ruler, the students will be instructed to draw a triangle. The group will decide who will draw an acute, obtuse, and right triangle. The students will cut out their triangles. 7. The teacher will instruct the students to color the angles of the triangle with different colors. 8. The student will cut off just the angles. 9. With a sheet of notebook paper, the teacher will instruct the students to place the angles with the point on the blue line. The angles should line up on the line. 10. The teacher will ask the question, “A line has what degree measure?” The response should be 180 degrees. 11. The teacher will elaborate that the angles are along the line, thus the angles together are 180 degrees. 12. The teacher will ask the groups to discuss, “What happens when the triangles are acute, obtuse or right?” The response is that all types of triangles will be 180 degrees. 13. The teacher will use the video on Youtube to review triangles and parallel lines. https://www.youtube.com/watch?v=bBt6IPkZd8 14. The teacher will hand out the worksheet, "Exterior Angles", from the attachments. 15. The teacher will monitor the students and check with each group to answer any questions. This is the informal assessment. 16. After completion of the worksheet, the students will move out of the groups. 17. The teacher will assign one student from each group to turn in the scissors and colored pencils or crayons. 18. Students will work independently on the worksheet for the formal assessment. The worksheet comes from the website Math Aids. http://www.mathaids.com/Geometry/Triangle/Triangle_Exterior_Angle_Theorem.html After: The students will complete an Exit Slip called 321. They will write the answers on the back of the worksheet. The teacher will write the following on the interactive whiteboard: 3 – List three things that you have learned today. 2 – List two things that you would like to know more about. 1 – Write a question from the material that you did not understand. 
Attachments: **Some files will display in a new window. Others will prompt you to download. 
Assessment Strategies 
Informal: The teacher will complete an informal assessment as he/she walks around the room monitoring the students. During the lesson, the teacher will randomly select students to determine if the student is engaged and understanding the material. Formal: The teacher will create an assessment sheet for the class using the website, http://www.mathaids.com/Geometry/Triangle/Triangle_Exterior_Angle_Theorem.html. The teacher will use the 321 exit slip to make an assessment about how well he/she presented the lesson. 
Acceleration: 
The accelerated student will be assigned a more challenging worksheet with multistep algebra problems. The worksheet is in the attachment section called "Exterior Angle Accelerated". 
Intervention: 
Students who require intervention can be placed with a peertutor. During the lesson, the teacher can work oneonone with the students. The teacher does have the option to reduce the number of problems or give the students more time to complete the assignment. 
View the Special Education resources for
instructional guidance in providing modifications and adaptations
for students with significant cognitive disabilities who qualify for the Alabama Alternate Assessment.
