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Geometry Notes
Section 1-4
9/11/07
What you’ll learn
How to measure and classify angles.
 How to identify and use congruent angles
and the bisector of an angle.

Vocabulary Terms:
Degree
 Ray
 Opposite rays
 Angles
 Sides of an angle
 Vertex of an angle
 Interior and exterior of an angle
 Right angle, obtuse angle, acute angle
 Angle bisector

Ray—a part of a line


Draw it with a dot (the endpt)
at one end and an arrow at
the other
Name it with the endpt and
one other pt on the ray
Fact: 2 opposite rays meet at
their endpts and make a
straight line
 Words/Symbols:

 PQ
P
Q
Two noncollinear rays intersecting
at their endpts make an. . .
Angle
Angle—formed by two noncollinear
rays that share a common endpt

Draw it with arrows

Name it by
A
3
noncollinear pts on the angle
(vertex in middle)
 The vertex
R
 a number

1
Words/Symbols:
 ART
 R
 1
T
 Facts:
the
2 rays are the sides
the common endpt is the vertex
angles are measured in
degrees
Everyone knows

Right angles measure 90º

Acute angles measure between 0º and 90º

Obtuse angles measure between 90º and
180º
Congruent Angles
Remember congruent means same shape
and size
 All angles have basically the same shape
(two noncollinear rays connected at a
common endpoint)
 To be congruent two angles must have the
same measure.
 Congruent angles will have identical marks

Congruent Angles have identical
marks. . .
1  2
1
2
Angle Bisectors-- rays that cut an
angle into two smaller congruent
angles
A

Draw it
T
B
C
BT bisects ABC so ABT TBC
Have you learned?
How to measure and classify angles.
 How to identify and use congruent angles
and the bisector of an angle.
 P. 34(13-47odd, 51-65odd)
