Download Angles - Benjamin N. Cardozo High School

Basics of Geometry
Angles
Rays are important because they help us define something very
important in geometry…Angles!
An angle consists of two different rays that have the same initial
point. The rays are sides of the angles. The initial point is called the
vertex.
Notation: We denote an angle with
vertex
B
sides
A
C
three points and  symbol. The
middle point is always the vertex.
We can also name the angle with
just the vertex point. This angle can
be denoted as:
BAC , CAB, or A
Classifying Angles
Basics of Geometry
Angles are classified as acute, right, obtuse, and straight,
according to their measures. Angles have measures greater
than 0° and less or equal to 180°.
A
A
A
Acute angle
Right angle
Obtuse angle
Straight angle
0°< m  A < 90°
m  A = 90°
90°< m  A < 180°
m  A = 180°
A
Interior & Exterior
of an Angle
Basics of Geometry
Basics of Geometry
Quick Quiz !!!!
Use the diagram below to answer the following questions.
S
a. Name the type of angle.
Acute
b. Name the vertex.
R
c. Name the sides of the angle.
RT and RS
d. Name the angle three different ways.
SRT , TRS , or R
R
T
Congruent Angles are angles
that have the same measure.
Either notation can be used:
Geometry Leeson:
Undefined Terms, Lines,
5
Basics of Geometry
An angle bisector is a ray whose endpoint
is the vertex of the angle, and that divides
that angle into two congruent angles.
In the figure below, OC is the bisector of
AOB and angle AOC is congruent to angle
COB.