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You identified and used special pairs of angles. 2-8 Proving Angle Relationships. Use the Angle Addition Postulate to find the measure of angles. Page 151 in your book. Protractor Postulate. - PowerPoint PPT Presentation
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2-8 Proving Angle Relationships
You identified and used special pairs of angles.
• Use the Angle Addition Postulate to find the measure of angles.
Page 151 in your book
Protractor PostulateDoes for angles what the
Ruler Postulate does for segments. It guarantees that any angle has exactly one measure. It also ensures that all angles measures are less than 180°.
Page 151 in your book
Angle addition postulate is like the segment addition postulate. This means we can add two angles together and they will equal the one big angle.
Try It
PRNmFind
QPRmandQRPm
.132,45
M R Q
N
P
87°
Try It
.
.137
DACmandBADmFind
BACmSuppose
A
B
C
D
3X°(4X−3)°
CONSTRUCTION Using a protractor, a construction worker measures that the angle a beam makes with a ceiling is 42°. What is the measure of the angle the beam makes with the wall?
The ceiling and the wall make a 90 angle. Let 1 be the angle between the beam and the ceiling. Let 2 be the angle between the beam and the wall.
m1 + m2 = 90 Angle Addition Postulate
42 + m2 = 90 m1 = 42
42 – 42 + m2 = 90 – 42 Subtraction Property of Equality
m2 = 48 SubstitutionAnswer: The beam makes a 48° angle
with the wall.
A. 32
B. 94
C. 104
D. 116
Find m1 if m2 = 58 and mJKL = 162.
Page 152 in your book.
A. 20
B. 30
C. 40
D. 50
QUILTING The diagram shows one square for a particular quilt pattern. If mBAC = mDAE = 20, and BAE is a right angle, find mCAD.
2-8 AssignmentPage 156, 8-13
Find the measure of
each numbered angle only.
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