Book description
Having trouble with geometry? Do Pi, The Pythagorean Theorem, and angle calculations just make your head spin? Relax. With Head First 2D Geometry, you'll master everything from triangles, quads and polygons to the timesaving secrets of similar and congruent angles  and it'll be quick, painless, and fun.
Through entertaining stories and practical examples from the world around you, this book takes you beyond boring problems. You'll actually use what you learn to make reallife decisions, like using angles and parallel lines to crack a mysterious CSI case. Put geometry to work for you, and nail your class exams along the way.
We think your time is too valuable to waste struggling with new concepts. Using the latest research in cognitive science and learning theory to craft a multisensory learning experience, Head First 2D Geometry uses a visuallyrich format designed for the way your brain works, not a textheavy approach that puts you to sleep.
Publisher resources
Table of contents
 Advance Praise for Head First 2D Geometry
 Praise for other Head First books
 Copyright
 Dedication
 The Authors
 Table of Contents (1/2)
 Table of Contents (2/2)
 How to Use this Book: Intro

Chapter 1: Finding Missing Angles: Reading Between the Lines
 There’s been a homicide
 In the ballistics lab you’ve got to cover all the angles
 Do the angles between Benny, Micky, and the bullet match up?
 Right angles aren’t always marked with numbers
 Angles can be made up of other, smaller angles
 Complementary angles always add up to a right angle (90º)
 Right angles often come in pairs
 Angles on a straight line add up to 180º
 Pairs of angles that add up to 180º are called supplementary angles
 Vertical angles are always equal
 The corner angles of a triangle always add up to a straight line
 Find one more angle to crack the case
 Something doesn’t add up!
 If it doesn’t all add up, then something isn’t as it seems
 You’ve proved that Benny couldn’t have shot Micky!
 We’ve got a new sketch—now for a new ballistics report
 We need a new theory
 Work out what you need to know
 Tick marks indicate equal angles
 Use what you know to find what you don’t know
 The angles of a foursided shape add up to 360º
 Parallel lines are lines at exactly the same angle
 Parallel lines often come with helpful angle shortcuts
 Great work—you cracked the case!
 Your Geometry Toolbox

Chapter 2: Similarity and Congruence: Shrink to Fit
 Welcome to myPod! You’re hired
 Liz wants you to etch her phone
 The designer noted some of the details
 The design tells us that some triangles are repeated
 Similar triangles don’t just look the same
 To use similarity, you need to be able to spot it
 You can spot similar triangles based on just two angles
 Employee of the month already?
 You sketch it—we’ll etch it!
 Fire up the etcher!
 The boss isn’t happy, but at least you’re not fired…
 It’s a problem of scale…
 Complex shapes can be similar, too
 You sketch it—we’ll etch it (to fit)
 Liz is back with a special request
 Similar shapes that are the same size are congruent
 Use what you know to find what you don’t know (1/2)
 Use what you know to find what you don’t know (2/2)
 Ratios can be more useful than sizes
 Ratios need to be consistent
 Your new design ROCKS!
 Your Geometry Toolbox

Chapter 3: The Pythagorean Theorem: All the Right Angles
 Giant constructionkit skate ramps
 Standardsizedquickassemblywhat?!?
 The ramps must have perpendicular uprights
 You can use accurate construction to test ramp designs on paper (1/2)
 You can use accurate construction to test ramp designs on paper (2/2)
 Not all lengths make a right triangle
 You can explore a geometry problem in different ways
 In geometry, the rules are the rules
 Any good jump has some similar scaled cousins
 The lengths of the sides are linked by a pattern
 The square of the longest side is equal to the squares of the other two sides added together
 The Pythagorean Theorem: a² + b² = c² (1/2)
 The Pythagorean Theorem: a² + b² = c² (2/2)
 Using Kwikklik skate ramps is definitely the right angle!
 A longer rope swings further and lower
 So, how far can you swing on a sixmeter rope?
 Your rope swing is perfect
 Your Geometry Toolbox

Chapter 4: Triangle Properties: Between a Rock Show and a Triangular Place
 Everybody loves organizing a rock festival
 First we need to pick a venue
 Fencing costs money
 Does a bigger perimeter mean a bigger area?
 How many people can each venue hold?
 A triangle fits inside a bounding rectangle (1/2)
 A triangle fits inside a bounding rectangle (2/2)
 The area of a triangle = 1/2 base × height
 You’ve got $11,250 to spend
 All speakers are not created equal
 So what are you looking for in your speakers?
 The ideal speakers are wider and longer than the venue…but only by a little
 100m will do, but can you rent the 60° speaker?
 The 60° speakers are spot on
 All that’s left is to pick a spot for the drinks stall
 A triangle has more than one center
 The center of a triangle can be outside the triangle
 Let’s put the drink stall at the centroid
 The rock festival is ready!
 The people behind the drinks stall won’t see the stage…
 You need a screen for less than $1,440
 Will the special offer screen still do the job?
 You can find area from sides using Hero’s formula
 Hero’s formula and “1/2 base × height” work together
 The rock festival is gonna…rock!
 Your Geometry Toolbox

Chapter 5: Circles: Going Round and Round
 It’s not just pizza—it’s war!
 How does MegaSlice’s deal measure up?
 The diameter of a circle is twice its radius
 How do slices compare to whole pizzas?
 Sectors of a circle have angles totaling 360°
 MegaSlice’s $10 deal is a con!
 Pepperoni crust pizza—but at what price?
 The pepperoni perimeter is 3 (and a bit) times diameter
 Mario wants to put your pepperoni crust pricing formula to the test
 The customers are always fussy
 An arc is a section of the circumference
 Mario’s business is booming!
 But MegaSlice is at it again...
 We need to find the area of the two pizza deals
 Each sector (slice) is a triangle (kind of)
 Area of a circle = πr²
 Mario’s pizza is here to stay
 Your Geometry Toolbox

Chapter 6: Quadrilaterals: It's Hip to be Square
 Edward’s Lawn Service needs your help
 Your first lawn
 The lawn is a parallelogram
 Let’s split the parallelogram
 Business is booming!
 If you don’t like what you’re given, change it
 But people are upset with Ed’s prices…
 Let’s compare the two lawns
 The lawns need edging, too
 Same shape, different perimeters
 Edward changed his rates…
 …and the customers keep flooding in
 Use diagonals to find the area of the kite
 Landowners, unite
 There are some familiar things about this shape
 Calculate trapezoid area using base length and height
 The quadrilateral family tree
 You’ve entered the big league
 Your Geometry Toolbox

Chapter 7: Regular Polygons: It's All Shaping Up
 We need to choose a hot tub
 All the hot tubs are regular polygons
 Regular polygons have equal sides and angles
 Buttspace is all about perimeter
 Is 3 cubic meters of water a lot or a little?
 Hot tub volume is area × depth
 The hot tub’s area must be 6m²
 Which hot tub shape gives the most buttspace?
 Work backward from area to find buttspace
 Is 19.6 butts a lot or a little?
 The square tub beats the circle tub
 Two tubs down, five to go
 You’ve found the formula for the area of an equilateral triangle
 Keep track of complex comparisons with a table (1/2)
 Keep track of complex comparisons with a table (2/2)
 Chop the polygons into triangles
 What do we need to know about the polygon triangles?
 The circles give us the properties we need
 Polygon area = 1/2 perimeter × apothem
 More sides = fewer butts
 Rock stars—high maintenance?
 Great tub choice!
 But what about dimensions?
 It’s time to relax in the hot tub!
 Your Geometry Toolbox
 Leaving town…
 It’s been great having you here in Geometryville!
 Index (1/2)
 Index (2/2)
Product information
 Title: Head First 2D Geometry
 Author(s):
 Release date: November 2009
 Publisher(s): O'Reilly Media, Inc.
 ISBN: 9780596808334
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