M217 Section 1.3
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Transcript of M217 Section 1.3
M217 Section 1.3
Measuring Angles
Angle Terminology:• Angle: 2 different rays with the
same endpoint• Vertex: Common endpoint - A• Sides: Two rays –• Naming:• Interior:• Exterior:• On:
AB and AC
C
A B
E
I2
Angle Measures, Congruency• Angles are measured using a protractor• If two angles have the same measure, then they are
congruent angles and are marked with arcs• the
A
B
CD
E
F
measure of angle A: m A
4
Classifying Angles by Measure
Term Definition ExampleAcute
Right
ObtuseStraight
Angle Addition Postulate
m PST
m RSP
S T
P
R• If P is on the interior of angle RST, then
• Basically: two parts = 1 whole
m RSP m PST m RST
T is on the interior of angle PQR1. 25
11Find
m PQRm RQTm PQT
2. (10 7)(5 )(4 6)
Find and
m PQR xm RQT xm PQT xx m PQR
Defn: Angle Bisector• An Angle Bisector is a ray that divides an
angle into two congruent angles
Angle Bisector3. bisects
(10 13)(6 1)
Find , and
QT PQRm RQT xm PQT xx m PQT m PQR
4. bisects (5 3)(12 4)
Find and
QT PQRm PQT ym PQR yy m TQR
Reading a Protractor• Notice two sets of
numbers
• Now try #4 – 6 on page 24. Then begin HW
4. 15◦, acute
5. 105 ◦, obtuse
6. 110 ◦, obtuse