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Head First 2D Geometry by Dawn Griffiths, Stray

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table of contents
Table of Contents (Summary)
Intro xvii
1 Finding missing angles: Reading between the lines 1
2 Similarity and congruence: Shrink to fit 49
3 The Pythagorean Theorem: All the right angles 103
4 Triangle properties: Between a rock show and a triangular place 149
5 Circles: Going round and round 205
6 Quadrilaterals: It’s hip to be square 235
7 Regular polygons: It’s all shaping up 273
Table of Contents (the real thing)
Intro
Your brain on Geometry. Here you are trying to learn something,
while here your brain is doing you a favor by making sure the learning doesn’t
stick. Your brain’s thinking, “Better leave room for more important things, like
which wild animals to avoid and whether naked snowboarding is a bad idea.
So, how do you trick your brain into thinking that your life depends on knowing
about triangles and circles and the Pythagorean Theorem?
Who is this book for? xviii
We know what you’re thinking xix
Metacognition: thinking about thinking xxi
Here’s what YOU can do to bend your brain into submission xxiii
Read me xxiv
The technical review team xxvi
Acknowledgments xxvii
ix
CHARLIE GREEN
HF COUNTY
SHERIFF’S OFFICE
table of contents
finding missing angles
Reading between the lines
1
Ever get the feeling there’s something they’re not
telling you?
If you want to master the real world, you need to get geometry. It’s a set of
tools for turning a little bit of information into a complete picture. Whether
you want to design something, build something or find out how a situation
really went down, geometry can make sure you’ve always got the lowdown.
So if you want to keep in the loop, grab your hat, pack your pencil, and join us
on the bus to Geometryville.
There’s been a homicide 2
In the ballistics lab you’ve got to cover all the angles 3
Do the angles between Benny, Micky, and the bullet match up? 4
Right angles aren’t always marked with numbers 6
Angles can be made up of other, smaller angles 7
Complementary angles always add up to a right angle (90º) 9
Right angles often come in pairs 11
Angles on a straight line add up to 180º 14
Pairs of angles that add up to 180º are called supplementary angles 17
Vertical angles are always equal 19
The corner angles of a triangle always add up to a straight line 20
18º
Find one more angle to crack the case 21
Something doesn’t add up! 23
If it doesn’t all add up, then something isn’t as it seems 24
You’ve proved that Benny couldn’t have shot Micky! 25
We’ve got a new sketch—now for a new ballistics report 26
We need a new theory 27
Work out what you need to know 29
Tick marks indicate equal angles 30
Use what you know to find what you don’t know 31
The angles of a four-sided shape add up to 360º 35
Parallel lines are lines at exactly the same angle 39
Parallel lines often come with helpful angle shortcuts 40
Great work—you cracked the case! 44
Your Geometry Toolbox 46
x

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