Download Lesson 7-5a

7-5
6th grade math
Classifying and Measuring Angles
Objective
• To draw, measure, and classify angles
• Why? To know how to correctly use a protractor
or name angles without a protractor. To help you
understand more geometry (see you in 9th
grade).
California State Standards
MG 2.1 (Gr 5): Measure, identify, and draw
angles, but using appropriate tools …
MR 1.0: Deepen your understanding of the
measurement of plane and solid shapes and use
this understanding to solve problems.
Vocabulary
• Point
– An exact location in space
•
.
X
• Line
– An endless collection of points along a straight path. A
line has no end points
•
. . . .
E F GH
• Line segment
– A part of a line having two endpoints
•
.
A
.
B
Vocabulary
• Ray
– A part of a line that has one endpoint and goes on and on in one
direction
.
• Angle
– Two rays with common endpoints called the vertex . Read with
.A
vertex in the middle. ∠ABC
.B
.C
• Vertex
– The common endpoint of the two rays that form the sides of an
angle. See above.
– The point of intersection of two sides of a polygon. . The point of
intersection of three edges of a space figure.
.
.
Vocabulary
• Plane
– A flat surface extending endlessly in all directions
• Protractor
– An instrument used to measure angles or draw
angles
• Congruent
– Same shape and same size
• ≈ is the symbol for congruent. Also seen above an equal
sign.
• Right angle
– An angle that measure 90°.
•
Classification
Vocabulary
Often has a ‘corner’ mark
┐
• Obtuse angle
– An angle that measures more than 90° and less than
180°
• Acute angle
– An angle that measure less than 90° and more than
0°
• Straight angle
– An angle with a measure of 180°
How to Measure with a Protractor
1)Observe is angle is
obtuse (past 90°) or
acute (less 90°)
2)Place hole in center of
protractor at vertex. Line
up ray with the 0° mark
3) If obtuse angle, read the
protractor’s measure
past 90°. If acute angle,
read the protractor’s
measure less 90°.
.
How to Draw with a Protractor
1)Observe is angle is obtuse
(past 90°) or acute (less
90°)
2)Place hole in center of
protractor at vertex. Line
up ray with the 0° mark
3) If obtuse angle, read the
protractor’s measure past
90°. If acute angle, read the
protractor’s measure less
90°.
*) Angles can be drawn in
any direction: left, right,
sideways; as long as
‘opening’ is correct
measurement.
.
Try It!
Measure and classify
1.
2.
3.
4.
1) ∠ ABC
50°, acute
2) ∠ XYZ
120°, obtuse
3) ∠ OPQ
68°, acute
4) ∠ DEF
117°, obtuse
Try Some More!
5) acute
6) obtuse
Draw and classify
5) 40°
6) 100°
7) 25°
8) 180°
9) At 3:00, what type of
angle is formed?
7) acute
8) straight
9) 90°
Objective Review
• To draw, measure, and
classify angles
• Why? You now know how to correctly use a
protractor or name angles without a
protractor.
• This will help you understand more geometry
(see you in 9th grade).
• Learning how to identify and label basic
geometric figures and how to classify,
measure, and draw angles can help you
understand basic geometric ideas and
relationships.
Independent Practice
• Complete problems 1021
• Copy original problem
first.
• Show all work!
• If time, complete Mixed
Review: 22-29
• If still more time, work
on Accelerated Math.