Exploring%20Angles

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Exploring Angles
A ray has one endpoint and extends indefinitely
in one direction.
An angle is a figure formed by two rays with a
common endpoint.
The two rays are called sides. The common point
is the vertex of the angle.
Vertex
Notation ltA , ltBAC, ltCAB, or lt 1

B
1
A
C
Angles can be measured in units called degrees
using a PROTRACTOR. Notation mltBAC, mltA, or
mltCAB
Sides
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Copy this site http//laika.ed.csuohio.edu/sum97/
bruehler/bruehler.html Useful to review geometry
glossary terms
Postulate 1-3 Protractor Postulate Given AB and
and a number R between 0 and 180, there is
exactly one ray with endpoint A extending on
either side of AB, such that the measure of the
angle formed is r.
Postulate 1-4. Angle Addition Postulate If R is
in the Interior of ltPQS, then mltPQR mltRQS
mltPQS. If mltPQR mltRQS mltPQS then R is in the
interior Of ltPQS
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Types of Angles
Angle A is a right angle if mltA is 90

• Right angle 90
• Acute angle lt90
• Obtuse angle gt90
• Straight angle 180

Angle A is an acute angle if mltA is less than 90
Angle A is a obtuse angle if mltA is greater than
90 and less than 180
Angle A is a straight angle if mltA is 180
.
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Congruent angles Angles that have the same
measure.
A
B
IF mltA mltB Then ltA ltB
?
.
An angle bisector divides the angle into two
congruent angles. Q PS is the
angle bisector P
S of ltPQR. Point S must be

in the interior of ltQPR,
R and ltQPS ltSPR
.
.
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