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Transcript
Geometry
Level 1
Angle names
Acute angle
Web animation
An acute angle is between 0 and 90 degrees
Angle names
Obtuse angle
Website animation
An obtuse angle is between 90 and 180
degrees
Angle names
Reflex angle
A reflex angle is between 180 and 360
degrees
Angle names
Right angle
A right angle is 90 degrees
Angle names
Right angle
A right angle is 90 degrees
Angle names
Straight angle
A straight line is 180 degrees
Naming angles
• The angle is at B
A
B
ABC
C
Guessing the angle size
• The clock is divided
into 12 hours.
• One complete circle
is 360 degrees.
• Each hour makes 30
degrees.
30

60

90

120

210

270

180

What angle do the hands of
the clock make?
• 4 lots of 30 degrees.
• 120 degrees.
• OR the reflex angle
is 240 degrees.
Guess the angle size
150
210
60
300
OR
90
270


170
190
Complementary angles
• Two angles which
add up to 90
degrees are said to
be complementary.
Complementary angles
• What is the
complement of 58
degrees?
?
Complementary angles
• 32 degrees
58  32  90
Complementary angles
• What is the
complement of 45
degrees?
?
?
Complementary angles
• 45 degrees
45  45  90
Supplementary angles
• Two angles which
add up to 180
degrees are said to
be supplementary.
Supplementary angles
• What is the
supplement of 120
degrees?
?
?
Supplementary angles
• 60 degrees?
?
Supplementary angles
• What is the
supplement of 40
degrees?
?
Supplementary angles
• What is the
supplement of 140
degrees?
Measuring angles
• We use a protractor
to measure angles.
There are two scales marked
on your protractor
First decide if your angle is
acute or obtuse
This angle is acute
Read the acute scale.
The angle is 56 degrees.
This angle is obtuse.
Read the obtuse scale.
The angle is 124 degrees.