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.
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=bBt6IPkZd-8
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.math-aids.com/Geometry/Triangle/Triangle_Exterior_Angle_Theorem.html
The students will complete an Exit Slip called 3-2-1. 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.