1. 6-3 Warm Up Problem of the Day Lesson Presentation
The Pythagorean Theorem
Warm Up
Problem of the Day
Lesson Presentation
Pre-Algebra

2. Pre-Algebra
6-3
The Pythagorean Theorem
Warm Up
Graph the figures with the given verticals and find the area.
1. (–1, –1), (–1, 3), (6, –1)
2. (2, 1), (8, 1), (6, –3)
3. (3, –2), (15, –2), (14, 6), (4, 6)
14 units2
12 units2
88 units2

3. Problem of the Day
A side of a square A is 5 times the length of square B. How many times as great is the area of square A than the area of square B? 25

4. 6-3
The Pythagorean Theorem
Learn to use the Pythagorean Theorem and its converse to solve problems.

5. Vocabulary
Pythagorean Theorem
leg
hypotenuse

6. a2 + b2 = c2

7. Additional Example 1A: Find the the Length of a Hypotenuse
Find the length of the hypotenuse. c A. 4 5
a2 + b2 = c2
Pythagorean Theorem
= c2
Substitute for a and b.
= c2
Simplify powers.
41 = c2
41 = c
Solve for c; c = c2.
6.40  c

8. Additional Example 1B: Find the the Length of a Hypotenuse
Find the length of the hypotenuse.
triangle with coordinates B.
(1, –2), (1, 7), and (13, –2)
a2 + b2 = c2
Pythagorean Theorem
= c2
Substitute for a and b.
= c2
Simplify powers.
225 = c
Solve for c; c = c2.
15 = c

9. Find the length of the hypotenuse.
Try This: Example 1A
Find the length of the hypotenuse. c A. 5 7
a2 + b2 = c2
Pythagorean Theorem
= c2
Substitute for a and b.
= c2
Simplify powers.
74 = c
Solve for c; c = c2.
8.60  c

10. Find the length of the hypotenuse.
Try This: Example 1B
Find the length of the hypotenuse.
B. triangle with coordinates (–2, –2), (–2, 4), and (3, –2) x y
(–2, 4)
The points form a right triangle.
a2 + b2 = c2
Pythagorean Theorem
= c2
Substitute for a and b.
= c2
Simplify powers.
(–2, –2)
(3, –2)
61 = c
Solve for c; c = c2.
7.81  c

11. Additional Example: 2 Finding the Length of a Leg in a Right Triangle
Solve for the unknown side in the right triangle.
a2 + b2 = c2
Pythagorean Theorem 25 b
72 + b2 = 252
Substitute for a and c.
49 + b2 = 625
Simplify powers.
– –49
b2 = 576 7
b = 24
576 = 24

12. Try This: Example 2 Solve for the unknown side in the right triangle.
a2 + b2 = c2
Pythagorean Theorem 12 b
42 + b2 = 122
Substitute for a and c.
16 + b2 = 144
Simplify powers.
– –16 4
b2 = 128
b  11.31
128  11.31

13. Additional Example 3: Using the Pythagorean Theorem to Find Area
Use the Pythagorean Theorem to find the height of the triangle. Then use the height to find the area of the triangle.
a2 + b2 = c2
Pythagorean Theorem
a = 62
Substitute for b and c.
a = 36 6 6 a
a2 = 20
a = units ≈ 4.47 units 4 4
Find the square root of both sides.
A = hb = (8)( 20) = units2  units2 1 2

14. Try This: Example 3
Use the Pythagorean Theorem to find the height of the triangle. Then use the height to find the area of the triangle.
a2 + b2 = c2
Pythagorean Theorem
a = 52
Substitute for b and c. 5 5
a2 + 4 = 25 a
a2 = 21
a = units ≈ 4.58 units 2 2
Find the square root of both sides.
A = hb = (4)( 21) = units2  4.58 units2 1 2

15. Lesson Quiz
Use the figure for Problems 1-3.
1. Find the height of the triangle. 8m
2. Find the length of side c to the nearest meter.
10 m c h
12m
3. Find the area of the largest triangle.
60m2
6 m
9 m
4. One leg of a right triangle is 48 units long, and the hypotenuse is 50 units long. How long is the other leg?
14 units