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Head First 2D Geometry
book

Head First 2D Geometry

by Stray (Lindsey Fallow), Dawn Griffiths
November 2009
Beginner content levelBeginner
368 pages
8h 55m
English
O'Reilly Media, Inc.
Content preview from Head First 2D Geometry
202 Chapter 4
your geometry toolbox
Your Geometry Toolbox
You’ve got Chapter 4 under
your belt and now you’ve
added properties of triangles
to your toolbox. For a complete
list of tool tips in the book, head to
www.headfirstlabs.com/geometry.
CHAPTER 4
Area =
1/2 base x height
The height comes from the
altitude of the triangle—it’s
perpendicular to the base.
Perimeter
Add up all the sides of
your shape to find the
perimeter.
Hero’s formula
Area = s (s-a) (s - b) (s - c)
s = a + b + c
2
Find the semiperimeter first,
then use it to find area.
Centroid
The point where all three
medians of the triangle
intersect
Median
A line from the midpoint of a
side to the opposite vertex
Incenter
The center of a circle drawn
inside the triangle, touching
every side
Circumcenter
The center of a circle drawn
outside the triangle, through
every vertex
Orthocenter
The point where all three
altitudes of the triangle
intersect
you are here 4 203
triangle properties
TriangleGrid Solution
Stop the press! Your buddies have secretly lined up
a headline act for the festival. Solve the grid puzzle
to be the rst to know who the mystery band are.
Clues
1. You use this theorem to find missing sides of right triangles.
2. Two angles adding up to 90º are known as this.
3. The month before August.
4. When lines cross, they create ...
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Publisher Resources

ISBN: 9780596808365Errata Page