1. 7.2 Use the Converse of the Pythagorean Theorem
7.2
Bell Thinger
1. Find x.
3. Find x.
ANSWER
29
2. Simplify (5
3 )2 .
ANSWER
ANSWER
75
9

2. 7.2

3. Example 1
7.2
Tell whether the given triangle is a right triangle.
a.
b.
Let c represent the length of the longest side of the
triangle. Check to see whether the side lengths satisfy
the equation c2 = a2 + b2.
a.
?
(3 34)2 = 92 + 152
?
9 34 = 81 + 225
306 = 306
The triangle is a right
triangle.
b.
?
262 = 222 + 142
?
676 = 484 + 196
676 = 680
The triangle is not a
right triangle.

4. Guided Practice
7.2
Tell whether a triangle with the given side lengths
is a right triangle.
1.
4, 4
3 ,8
ANSWER
2.
10, 11, and 14
ANSWER
3.
right triangle
5,6 and
ANSWER
not a right triangle
61
right triangle

5. 7.2

6. Example 2
7.2
Can segments with lengths of 4.3 feet, 5.2 feet, and
6.1 feet form a triangle? If so, would the triangle be
acute, right, or obtuse?
SOLUTION
STEP 1 Use the Triangle Inequality Theorem to
check that the segments can make a triangle.
4.3 + 5.2 = 9.5
9.5 > 6.1
4.3 + 6.1 = 10.4
10.4 > 5.2
5.2 + 6.1 = 11.3
11.3 > 4.3
The side lengths 4.3 feet, 5.2 feet, and 6.1 feet can
form a triangle.

7. Example 2
7.2
STEP 2 Classify the triangle by comparing the square
of the length of the longest side with the sum of
squares of the lengths of the shorter sides.
c2 ? a2 + b2
6.12 ? 4.32 + 5.22
37.212 ? 18.492 + 27.042
37.21 < 45.53
Compare c2 with a2 + b2.
Substitute.
Simplify.
c2 is less than a2 + b2.
The side lengths 4.3 feet, 5.2 feet, and 6.1 feet
form an acute triangle.

8. Example 3
7.2
Catamaran You are part of a crew
that is installing the mast on a
catamaran. When the mast is fastened
properly, it is perpendicular to the
trampoline deck. How can you check
that the mast is perpendicular using a
tape measure?
SOLUTION
To show a line is perpendicular to a plane you must show
that the line is perpendicular to two lines in the plane.

9. Example 3
7.2
Think of the mast as a line and the deck as a plane.
Use a 3-4-5 right triangle and the Converse of the
Pythagorean Theorem to show that the mast is
perpendicular to different lines on the deck.
First place a mark
3 feet up the mast
and a mark on the
deck 4 feet from the
mast.
Use the tape measure
to check that the
distance between the
two marks is 5 feet.
The mast makes a
right angle with the
line on the deck.
Finally, repeat the
procedure to show
that the mast is
perpendicular to
another line on the
deck.

10. Guided Practice
7.2
4. Show that segments with lengths 3, 4, and 6 can
form a triangle and classify the triangle as acute,
right, or obtuse.
ANSWER
3 + 4 > 6, 4 + 6 > 3, 6 + 3 > 4, obtuse

11. 7.2

12. Exit Slip
7.2
1.
Tell whether the triangle is a right triangle.
ANSWER
yes

13. Exit Slip
7.2
Decide if the segment lengths can form a triangle. If
so, tell whether the triangle is acute, right, or obtuse.
2.
7, 11,3 17
ANSWER
3.
yes; acute because 153 < 170.
4.1, 9.2, 5.6
ANSWER
yes; obtuse because 84.64 > 48.17.

14. Exit Slip
7.2
4.
A playground has a
slide, a swing and a
sandbox. The slide and
the swing are 32 feet
apart, the swing and the
sandbox are 50 feet
apart, and the slide and
sandbox are 48 feet apart.
Do the three pieces of
apparatus form a right
triangle?
ANSWER
no

15. 7.2
Homework
Pg 462-465
#12, 20, 21, 23, 28