9th Grade Law Of Cosine Lesson Plan Example (Math)

Topic: LAWS OF COSINE

Objectives & Outcomes

• Understand and be able to apply the laws of cosine in solving problems.

Materials

• Graph paper
• Pencils
• Calculator (optional)

Warm-up

• Ask the students to recall what the cosine of an angle is. Allow them to use their notes or the Internet for reference.
• Ask the students to give examples of problems that can be solved using the cosine law.

Direct Instruction

• Write the cosine law on the board:
• For any triangle, the sum of the squares of the lengths of the sides is equal to the square of the length of the third side times the cosine of the angle between those sides.
• Provide examples of how to use the cosine law to solve problems. For example, using the cosine law to solve for the third side of a triangle when given the other two sides and the angle between them.

Guided Practice

• Provide students with problems to solve using the cosine law. For example, provide a diagram of a triangle and have students use the cosine law to solve for one or more of the unknown sides or angles.

Independent Practice

• Provide students with a worksheet or online activity that includes problems for them to solve using the cosine law. These problems can be direct applications of the law or they can be problems that require the students to use the law in a more creative way (e.g., finding an angle that corresponds to a given side length or solving for multiple unknowns).

Closure

• Review the key ideas and definitions from the lesson.
• Ask students to share their solutions to the problems they solved and discuss any challenges they faced and how they resolved them.

Assessment

• Use the solutions students shared during the guided and independent practice to assess their ability to solve problems and use the law of cosine to find the angle in a triangle.