Lesson Plan: Pythagorean Theorem
Subject: Mathematics
Grade Level: 8
Duration: 30 Minutes
Objective
Students will understand the Pythagorean Theorem and how to apply it to find the lengths of sides in right triangles.
Materials Needed
- Whiteboard and markers
- Graph paper
- Ruler
- Protractor
- Worksheets with practice problems
Lesson Outline
Introduction (5 minutes)
- Begin with a question: “What do you know about right triangles?”
- Discuss the properties of right triangles and introduce the Pythagorean theorem:
- The theorem states that in a right triangle, the square of the length of the hypotenuse (c) is equal to the sum of the squares of the lengths of the other two sides (a and b).
- Mathematically, this is represented as:
[ c^2 = a^2 + b^2 ]
Explanation and Demonstration (10 minutes)
- Provide examples on the whiteboard.
- Example 1
- Given a right triangle with legs of lengths 3 cm and 4 cm, calculate the hypotenuse.
- Calculation:
[ c^2 = 3^2 + 4^2 ]
[ c^2 = 9 + 16 ]
[ c^2 = 25 ]
[ c = 5 ]
- Example 2
- Given a hypotenuse length of 10 cm and a leg of 6 cm, find the length of the other leg.
- Calculation:
[ 10^2 = 6^2 + b^2 ]
[ 100 = 36 + b^2 ]
[ b^2 = 64 ]
[ b = 8 ]
Guided Practice (10 minutes)
- Distribute graph paper and have students draw a right triangle with given leg lengths (for example, 5 cm and 12 cm).
- In pairs, have them calculate the hypotenuse using the Pythagorean theorem and then verify their results with a ruler.
Independent Practice (5 minutes)
Conclusion (5 minutes)
- Recap the Pythagorean theorem and its applications.
- Ask a few students to share their answers from the independent practice and discuss any challenges encountered.
Homework
Homework Assignment
Complete the following problems at home:
- A right triangle has legs measuring 7 cm and 24 cm. What is the length of the hypotenuse?
- If one leg of a right triangle is 8 cm and the hypotenuse is 10 cm, find the length of the other leg.
- The legs of a right triangle measure 9 cm and 12 cm. Check if it is a right triangle using the Pythagorean theorem.
Answers
-
Hypotenuse:
[ c^2 = 7^2 + 24^2 ]
[ c^2 = 49 + 576 ]
[ c^2 = 625 ]
[ c = 25 \, \text{cm} ]
-
Other leg:
[ 10^2 = 8^2 + b^2 ]
[ 100 = 64 + b^2 ]
[ b^2 = 36 ]
[ b = 6 \, \text{cm} ]
-
Check:
[ c^2 = 9^2 + 12^2 ]
[ c^2 = 81 + 144 ]
[ c^2 = 225 ]
- Yes, it is a right triangle since ( c = 15 \, \text{cm} ) (using ( 15^2 = 225 )).
Reflection
After conducting the lesson, reflect on student engagement and understanding of the Pythagorean theorem. Assess whether adjustments are needed for future classes.