Skip to Main Content
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 4 221
circles
An arc is a section of the circumference
Covering part of the pizza crust with pepperoni creates an arc. That’s
geometry jargon for a section of the circumference of a circle—whether
it goes almost all the way around a circle, or just a tiny part of it.
Arcs can be described by the proportion of the circumference they
cover—a semicircle covers half—or by the angle of the corresponding
sector (the arc is the outside curved part of the sector).
Arc length is circumference x sector angle / 360
o
To find the length of an arc, first you need to find the circumference of
the circle the arc is part of. That means that you need either the diameter
or radius of the circle. Then you can use the sector angle to find out the
length of the part of the circumference that your arc covers.
144º
I describe myself
as “four tenths
of a circle.”
170º
I think of myself as
a 170 degree arc.
144
360
Arc Length = 2
π
r × Sector Angle
360°
This calculation helps you find the
fraction of the circle that the
sector represents. If you already
know it’s 2/5 or 1/12, then just use
the fraction instead!
Sometimes arcs are described
as fractions. If you only
know the arc angle, then
you have to work out the
fraction.
4
10
=
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

Make: Geometry

Make: Geometry

Joan Horvath, Rich Cameron
Classical Geometry: Euclidean, Transformational, Inversive, and Projective

Classical Geometry: Euclidean, Transformational, Inversive, and Projective

I. E. Leonard, J. E. Lewis, A. C. F. Liu, G. W. Tokarsky

Publisher Resources

ISBN: 9780596808365Errata Page