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Head First 2D Geometry by Dawn Griffiths, Stray

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you’re promoted!
Great work—you cracked the case!
Thanks to your work uncovering the angles,
the right guy is behind bars.
You’ve mastered a whole bunch of techniques for finding
missing angles, uncovered some “sketchy” assumptions,
and discovered general rules that the CSI team can use
again and again to test out ballistics evidence. Your hard
work and talent hasn’t gone unnoticed—time to hang up
your lab coat and take a hot promotion!
CHARLIE GREEN
HF COUNTY
SHERIFF’S OFFICE
GEO180
C
harlie is gonna be making a
lot of lic
ense pl
a
tes....
44 Chapter 1
Before you collect your bonus and your new CSI
badge, the chief would appreciate it if you left
the ballistics lab a cheat sheet about how you
worked out who shot Micky.
We’re really impressed with how you
unravelled the evidence—this was a tricky
one! You’ve been great in the ballistics lab and
now you’ve proved you’re ready to become our
lead CSI, working your own important cases.
T
he chi
ef couldn’t be
happi
er wi
th y
ou.
finding missing angles
Angles in a triangle add
up to 180º
Match each technique for finding missing angles to a sketch. You can use
each technique just once, but some sketches will need more than one to
find the missing angle.
Vertical angles are equal
Parallel lines cross other
lines at the same angles
Angles on a straight line add
up to 180º
Angles in a four-sided
shape add up to 360º
Angles in a right angle add
up to 90º
73º
105º
93º
101º
32º
56º
62º
Answers on page 48.
you are here 4 45

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