Transcript Lesson 1 Contents

Lesson 1-4
Angle Measure
Transparency 1-4
5-Minute Check on Lesson 1-3
Use the number line to find each measure.
D
1. AC
-4
2. DE
-2
A
0
E
C
2
4
6
3. Find the midpoint of EG
8
D
10
E
F
G
H
4. Find the distance between P (-2,5) and Q (4,-3).
5. Find the coordinates of R, if M (-4,5) is the midpoint of RS and S has
coordinates of (0,-10)?
6.
What is the perimeter of ∆ DEF if its vertices are
D(-2,-6), E(-2,6), and F(3,-6)?
Standardized Test Practice:
A
12 units
B
13 units
C
17 units
Click the mouse button or press the
Space Bar to display the answers.
D
30 units
Transparency 1-4
5-Minute Check on Lesson 1-3
Use the number line to find each measure.
1. AC
4
2. DE
9
D
-4
3. Find the midpoint of EG
-2
A
0
E
C
2
4
6
F
8
D
10
E
F
G
H
4. Find the distance between P (-2,5) and Q (4,-3). 10
5. Find the coordinates of R, if M (-4,5) is the midpoint of RS and S has
coordinates of (0,-10)?
(-8, 20)
6.
What is the perimeter of ∆ DEF if its vertices are
D(-2,-6), E(-2,6), and F(3,-6)?
Standardized Test Practice:
A
12 units
B
13 units
C
17 units
Click the mouse button or press the
Space Bar to display the answers.
D
30 units
Objectives
• Measure and classify angles
• Identify and use congruent angles and the
bisector of an angle
Vocabulary
• Degree – one three hundred and sixtieth of a circle
• Ray – part of a line with one end point
• Opposite rays – are collinear rays with the same end
point (& form a 180 degree angle)
Angle is formed by 2 noncollinear rays with a common
endpoint (vertex)
• Sides – composed of rays
• Vertex – is the common endpoint
• Interior – area between the two rays that form the
angle
• Exterior – area not between the two rays that form
the angle
Vocabulary (cont)
Special types of angles:
• Right angle – measure equals 90 degrees
• Acute angle – measure is less than 90 degrees
• Obtuse angle – measure is greater than 90 degrees
(but less than 180)
• Angle Bisector – a ray that divides an angle into two
congruent angles
Angles
360º
A
Exterior of angle
Circle
Vertex
(hinge point)
Interior of angle
AVB
Ray VB
B
Angles measured in degrees
A degree is 1/360th around a circle
Acute
A
mA < 90º
Right
Obtuse
A
A
mA = 90º
90º < mA < 180º
Name all angles that have B as a vertex.
Answer: 5, 6, 7, and ABG
Name the sides of 5.
Answer:
and
or
are the sides of 5.
Write another name for 6.
Answer: EBD, FBD, DBF, and DBE
are other names for 6.
a. Name all angles that have X as a vertex.
Answer: 1, 2, 3, and RXB
or RXN
b. Name the sides of 3.
Answer:
c. Write another name for 3.
Answer: AXB, AXN, NXA, BXA
Measure TYV and classify it as
right, acute, or obtuse.
TYV is marked with
a right angle symbol,
so measuring is not
necessary.
Answer:
is a right angle.
Measure WYT and classify it as
right, acute, or obtuse.
Use a protractor to find
that
.
Answer:
>
is an obtuse angle.
With lines ZE and CX and ray ZD, measure each angle
named and classify it as right, acute, or obtuse.
a. CZD
Answer: 150, obtuse
E
D
b. CZE
X
C
Answer: 90, right
c. DZX
Answer: 30, acute
Z
SIGNS A railroad crossing sign forms congruent
angles. In the figure, WVX = ZVY. If mWVX =7a + 13
and mZVY =10a – 20, find the actual measurements of
WVX and ZVY.
WVX  ZVY
7a + 13 = 10a – 20
7a + 33 = 10a
33 = 3a
11 = a
WVX = 7(11) + 13 = 90°
Answer: Both WVX and ZVY measure 90°
Summary & Homework
• Summary:
– Angles are classified as acute, right, or
obtuse according to their measure
– An angle bisector is a ray that divides an
angle into two congruent angles (halves)
• Homework: pg 33-35;
9, 11, 13, 14, 20, 24-26, 50