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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
you are here 4 315
regular polygons
It’s a regular polygon, so the angles are equal = 720º = 120º
But what about dimensions?
Phew! The only thing left on your to-do list is to tell the carpenters
what length each side of the hot tub is.
Hint—look back at page 293 if you’re not sure where to start....
The total area of the hot tub is 6 square meters. Use what
you know about the hexagon hot tub angles to find the length
of each side of the hot tub. (Hint: it helps if you split it into
those sector triangles!)
This is what the carpenter
needs to know.
316 Chapter 7
brain barbell solution
These 6 triangles are the same (congruent). Each one must have
an area of 1 square meter.
The angles in the middle add up to 360º, so this angle here must
be 60º.
Each internal angle is 120º—and we know the triangle is
ISOSCELES because the side lengths are both equal to the
circumradius of the polygon, so the other angles must both be
120º/2 = 60º.
Each 1 sq meter triangle is EQUILATERAL.
So we can use the equilateral triangle area formula!
The total area of the hot tub is 6 square meters. Use what
you know about the hexagon hot tub angles to find the length
of each side of the hot tub.
Solution
60º
60º
3t
2
4
3t
2
4
4
3
Area =
1m
2
=
= t
2
2.31 = t
2
1.52m = t
Length of each side.
t is side length.
An isosceles triangle ...
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Publisher Resources

ISBN: 9780596808365Errata Page