Head First 2D Geometry

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

?º

105º

93º

101º

?º

32º

?º

56º

62º

?º

Answers on page 48.

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