Grade: 8 Subject: Mathematics Topic: Finding Angles in a Triangle

Objective: - Students will be able to identify and understand the different types of angles in a triangle. - Students will be able to apply the angle sum property of a triangle to find missing angles. - Students will be able to solve problems involving angles in triangles.

Materials: - Whiteboard or blackboard - Markers or chalk - Triangle cutouts or printed triangle images - Protractors - Worksheets with triangle problems - Rulers

Procedure:

1. Introduction (10 minutes):
   • Begin the lesson by asking students if they know what a triangle is and how many sides and angles it has.
   • Write the definition of a triangle on the board: “A triangle is a polygon with three sides and three angles.”
   • Show different triangle images on the board and ask students to identify the angles in each triangle.
2. Types of Angles in a Triangle (15 minutes):
   • Introduce the three types of angles in a triangle: acute, obtuse, and right angles.
   • Define each type of angle and provide examples on the board.
   • Discuss the sum of the angles in a triangle, which is always 180 degrees.
   • Write the angle sum property on the board: “The sum of the three angles in a triangle is always 180 degrees.”
3. Angle Sum Property (15 minutes):
   • Provide triangle cutouts or printed triangle images to each student.
   • Ask students to measure the angles of their triangles using protractors.
   • Instruct students to add up the three angles of their triangles and check if the sum is 180 degrees.
   • Discuss the results as a class and emphasize the angle sum property.
4. Finding Missing Angles (20 minutes):
   • Distribute worksheets with triangle problems to each student.
   • Instruct students to solve the problems by applying the angle sum property.
   • Encourage students to draw diagrams and label the given angles and unknown angles.
   • Circulate the classroom to provide assistance and guidance as needed.
5. Group Activity (15 minutes):
   • Divide the class into small groups of 3-4 students.
   • Provide each group with a large triangle cutout or printed triangle image.
   • Instruct the groups to measure and label the angles of their triangles.
   • Ask each group to find a missing angle in their triangle and explain their solution to the class.
6. Conclusion and Recap (5 minutes):
   • Summarize the key points discussed in the lesson, including the types of angles in a triangle and the angle sum property.
   • Ask students if they have any questions or if there are any concepts they would like to review.
   • Assign homework exercises or additional practice problems related to finding angles in triangles.

Assessment: - Observe students’ participation and engagement during class activities. - Review students’ completed worksheets and group activity solutions. - Assign homework exercises to assess individual understanding. - Conduct a short quiz or exit ticket to evaluate students’ comprehension of the topic.