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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
trapezoids have only two parallel sides
262 Chapter 6
There are some familiar things about
this shape
It’s a four-sided shape, but it only has one pair of parallel sides.
These parallel sides are called bases. We call this shape a
trapezoid.
A trapezoid
has exactly one
pair of opposite
parallel sides.
But what’s the area?
In theory, we could split the trapezoid into a rectangle and two
right triangles, and then add together the area of each shape. The
trouble is, we don’t have enough information to do this. We know
that they’re both right triangles, but we don’t know what the other
two angles are, and we only know the length of one of the sides. So
what can we do instead?
The bases here
are parallel.
Since the bases are
parallel, the angles
here are supplementary
(remember your F, N,
and Z patterns?).
24 meters
28 meters
53 meters
24 meters
…but we can’t work out the
area of the triangles because
we don’t know enough side
lengths.
We can split the trapezoid
into simpler shapes…
you are here 4 263
quadrilaterals
Instead of splitting the shape up, let’s add to it and see if that
helps us figure out how to find the area of a trapezoid. Here are
two congruent trapezoids. Draw them together so that they form
a single parallelogram.
What’s the width of the parallelogram?
What’s the height of ...
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Publisher Resources

ISBN: 9780596808365Errata Page