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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
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finding missing angles
Vertical angles are always equal
When two straight lines cross they always create two pairs of
equal opposite angles, called vertical angles.
Each angle has to form a supplementary pair with either of
the angles on the other side of it, so they must be equal.
These two
are equal.
These two are
also equal.
So if you know
this one…
…you already know
this one, too!
Save yourself a ton of
math by spotting equal
pairs of vertical angles.
Patterns in geometry aren’t just coincidence
These relationships are how geometry works…and to see a
really freaky one, try this:
On some scrap paper, draw a triangle using a ruler.
Cut the triangle out.
Tear the corners off.
And then put the three corner pieces together with
the points in the middle.
Weird, huh?
Do this!
Two straight
lines cross
Add either to the original
angle and you get 180º.
Pick one
angle
The supplements
must be equal
Find its
supplements
&
&
This is one
supplement…
…and here’s the
other one.
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Publisher Resources

ISBN: 9780596808365Errata Page