Angle Classification
Objectives
Key points
Warm-up
Stations
Wrap-up
Homework
Objectives
 TSWBAT classify angles as acute, obtuse, and right.
 TSWBAT recognize, explain, and use complementary and supplementary angles.
Key points
Link to GSP file of Angle Classifications

Acute angles are less than 90º
B
BAC is an acute angle
A

C
Obtuse angles are greater than 90º
G
GEF is an obtuse angle
E
F

Right angles are exactly 90º
K
KHJ is a right angle
The square in the corner indicates
the rays are perpendicular.
H

J
Complementary angles are two adjacent angles that together form a right (90º) angle
P
N
L

PLN and NLM are complementary
mPLN + mNLM = 90
M
Supplementary angles are two adjacent angles that together form a straight line (180º
angle)
Z
X
W
Y
XWZ and ZWY are supplementary and form XY
mXWZ + mZWY = 180
Warm-up (5-10 minutes)
Meet with your group from yesterday and be prepared to present when the buzzer sounds.
Your group will have 5 minutes to present all four products.
Presentations (20-25 minutes)
On SMART Board with projector
Teacher/students may comment with SMART notes after presentations
Definitions/Demonstration – word wall, definitions as above
Stations (5-10 minutes each, extended time for inclusion)
1. Demonstrate acute, obtuse, and right angles on SMART Board, allowing students to test
angles interactively. Show how angles with constraints are constructed. Teacher-led
roundtable discussion
2. Update online journal with last night’s homework journal entry: Where do you see
parallel and perpendicular lines in the “real world”? How would you explain to a new
student the differences between lines, segments, and rays?
3. Complementary and Supplementary Angle Puzzles
Using the angles provided, find complementary and supplementary angle pairs.
(see linked angle puzzles)
When not at a station
1. Check last night’s homework
2. Work on p. 31: 27 – 34
3. Write new journal entry: Find a “clever” way to remember complementary angles vs.
supplementary angles.
Example: complementary = completely 90, supplementary = straight
Wrap-up (< 5 minutes)
Reminder: Quiz tomorrow over linear objects; parallel, perpendicular, and skew lines; and
angle classification
Homework
Finish p. 31: 27 – 34 and journal entry: Find a “clever” way to remember complementary angles
vs. supplementary angles.