November 2009
Beginner
368 pages
8h 55m
English
Content preview from Head First 2D Geometry
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you are here 4 9
finding missing angles
Complementary angles always
add up to a right angle (90º)
If two angles combine to creat a right angle we call them
complementary angles. Usually, complementary angles are adjacent
(next to each other), but they can be any two angles anywhere that
add up to 90 degrees.
We say that the angles complement each other.
72º
18º “complements” 72º.
18º + 72º = 90º
so these angles are
complementary.
Draw lines to connect up five pairs of complementary angles.
You’ll have two lonely single angles left over. Can you work out their complements?
Hint: Your second answer might be surprising.
46º
52º
44º
9º
11º
79º
38º
27º
63º
40º
102º
50º
18º
72º
18º
They’re still
complementary, even if
they’re apart.
(And they’re
complimentary, too!)
Hey, you look nice
today!
Thanks! Not
so bad yourself....
10 Chapter 1
only acute angles can be complementary
46º
52º
44º
9º
11º
79º
38º
27º
63º
40º
102º
50º
Draw lines to connect up five pairs of complementary angles.
You’ll have two lonely single angles left over. Can you work out their complements?
46º + 44º = 90º
52º + 38º = 90º
40º + 50º = 90º
79º + 11º = 90º
63º + 27º = 90º
This angle doesn’t have a
complement because it is
already bigger than 90º!
90º - 9º = 81º, so the complement
of this angle would be 81º.
Did this surprise you?
Q:
How can I tell which a ...
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