1. The Pythagorean Theorem
9-8
The Pythagorean Theorem
Course 2
Warm Up
Problem of the Day
Lesson Presentation

2. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
Warm Up
Estimate each square root to the nearest whole number. Use a calculator to check the reasonableness of your answers. 1. 2. 3. 4
√18
√26 5
√86 9 4.
√125 11

3. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
Problem of the Day
A shipping carton measures 12 in. by 15 in. by 16 in. What is the longest rod that can be shipped in it?
25 in.

4. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
Learn to use the Pythagorean Theorem to find the length of a side of a right triangle.

5. Insert Lesson Title Here
Course 2
9-8
The Pythagorean Theorem
Insert Lesson Title Here
Vocabulary
leg
hypotenuse
Pythagorean Theorem

6. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
In a right triangle, the two sides that form the right angle are called legs. The side opposite the right angle is called the hypotenuse.
Hypotenuse
Leg
Leg
One of the first people to recognize the relationship between the sides of a right triangle was the Greek mathematician Pythagoras. This special relationship is called the Pythagorean Theorem.

7. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
PYTHAGOREAN THEOREM
In a right triangle, the sum of the squares of the lengths of the legs is equal to the square of the length of the hypotenuse.
a2 + b2 = c2 a c b
You can use the Pythagorean Theorem to find the length of any side of a right triangle.

8. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
Additional Example 1A: Calculating the Length of a Side of a Right Triangle
Use the Pythagorean Theorem to find the missing measure. c
12 cm
16 cm
a2 + b2 = c2
Use the Pythagorean Theorem.
= c2
Substitute for a and b.
= c2
Evaluate the powers.
400 = c2
Add.
√400 = √c2
Take the square root of both sides.
20 = c
The length of the hypotenuse is 20 cm.

9. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
Additional Example 1B: Calculating the Length of a Missing Side of a Right Triangle
Use the Pythagorean Theorem to find the missing measure. b
5 cm
13 cm
a2 + b2 = c2
Use the Pythagorean Theorem.
52 + b2 = 132
Substitute for a and c.
25 + b2 = 169
Evaluate the powers.
–25
–25
Subtract 25 from each side.
b2 = 144
√b2 = √144
Take the square root of both sides.
b = 12
The length of the missing leg is 12 cm.

10. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
Check It Out: Example 1A
Use the Pythagorean Theorem to find the missing measure.
11 cm c
15 cm
a2 + b2 = c2
Use the Pythagorean Theorem.
= c2
Substitute for a and b.
= c2
Evaluate the powers.
346 = c2
Add.
√346 = √c2
Take the square root of both sides.
18.6  c
The length of the hypotenuse is about 18.6 cm.

11. The Pythagorean Theorem
Course 2
9-8
The Pythagorean Theorem
Check It Out: Example 1B
Use the Pythagorean Theorem to find the missing measure. b
3 cm
5 cm
a2 + b2 = c2
Use the Pythagorean Theorem.
32 + b2 = 52
Substitute for a and c.
9 + b2 = 25
Evaluate the powers. –9 –9
Subtract 9 from each side.
b2 = 16
√b2 = √ 16
Take the square root of both sides.
b = 4
The length of the missing leg is 4 cm.

12. Additional Example 2: Problem Solving Application
Course 2
9-8
The Pythagorean Theorem
Additional Example 2: Problem Solving Application
A square field has sides of 75 feet. About how far is it from one corner of the field to the opposite corner of the field? Round your answer to the nearest tenth.

13. Understand the Problem
Course 2
9-8
The Pythagorean Theorem
Additional Example 2 Continued 1
Understand the Problem
Rewrite the question as a statement.
• Find the distance from one corner of the field
to the opposite corner of the field.
List the important information:
• Drawing a segment from one corner of the field to the opposite corner of the field divides the field into two right triangles.
• The segment between the two corners is
the hypotenuse.
• The sides of the field are legs, and they
are each 75 feet long.

14. Additional Example 2 Continued
Course 2
9-8
The Pythagorean Theorem
Additional Example 2 Continued 2
Make a Plan
You can use the Pythagorean Theorem to
write an equation.

15. Additional Example 2 Continued
Course 2
9-8
The Pythagorean Theorem
Additional Example 2 Continued
Solve 3
a2 + b2 = c2
Use the Pythagorean Theorem.
= c2
Substitute for the known variables.
5, ,625 = c2
Evaluate the powers.
11,250 = c2
Add.
 c
Take the square roots of both sides.
106.1  c
Round.
The distance from one corner of the field to the
opposite corner is about feet

16. Additional Example 2 Continued
Course 2
9-8
The Pythagorean Theorem
Additional Example 2 Continued 4
Look Back
The hypotenuse is the longest side of a right triangle. Since the distance from one corner of the field to the opposite corner is greater than the length of a side of the field, the answer is reasonable.

17. Understand the Problem
Course 2
9-8
The Pythagorean Theorem
Insert Lesson Title Here
Check It Out: Example 2
A rectangular field has a length of 100 yards and a width of 33 yards. About how far is it from one corner of the field to the opposite corner of the field? Round your answer to the nearest tenth. 1
Understand the Problem
Rewrite the question as a statement.
• Find the distance from one corner of the field to the opposite corner of the field.

18. Check It Out: Example 2 Continued
Course 2
9-8
The Pythagorean Theorem
Check It Out: Example 2 Continued
List the important information:
• Drawing a segment from one corner of the field
to the opposite corner of the field divides the field into two right triangles.
• The segment between the two corners is
the hypotenuse.
• The sides of the fields are legs, and they are 33 yards long and 100 yards long. 2
Make a Plan
You can use the Pythagorean Theorem to
write an equation.

19. The Pythagorean Theorem Insert Lesson Title Here
Course 2
9-8
The Pythagorean Theorem
Insert Lesson Title Here
Check It Out: Example 2 Continued
Solve 3
a2 + b2 = c2
Use the Pythagorean Theorem.
= c2
Substitute for the known variables.
,000 = c2
Evaluate the powers.
11,089 = c2
Add.
 c
Take the square roots of both sides.
105.3  c
Round.
The distance from one corner of the field to the
opposite corner is about yards.

20. The Pythagorean Theorem Insert Lesson Title Here
Course 2
9-8
The Pythagorean Theorem
Insert Lesson Title Here
Check It Out: Example 2 Continued 4
Look Back
The hypotenuse is the longest side of a right triangle. Since the distance from one corner of the field to the opposite corner is greater than the length of either side of the field, the answer is reasonable.

21. The Pythagorean Theorem Insert Lesson Title Here
Course 2
9-8
The Pythagorean Theorem
Insert Lesson Title Here
Lesson Quiz: Part I
Use the Pythagorean Theorem to find each missing measure. 1. 2.
21 in.
40 m
3. a = , b = 30, c = 34 16
4. a = 20, b = 21, c = 29

22. The Pythagorean Theorem Insert Lesson Title Here
Course 2
9-8
The Pythagorean Theorem
Insert Lesson Title Here
Lesson Quiz: Part II
5. Each rectangular section of a fence is braced by a board nailed on the diagonal of the section. The fence is 6 ft tall and the brace is 10 ft long. What is the length of the section?
8 ft