
100 Chapter 2
your geometry toolbox
Your Geometry Toolbox
You’ve got Chapter 2
under your belt and now
you’ve added Similarity and
Congruence to your toolbox. For a
complete list of tool tips in the book,
visit www.headfirstlabs.com/geometry.
CHAPTER 2
Similar shapes have
equal angles.
Similar shapes have
the same ratios
between side lengths.
You can spot similar triangles
from two equal angles.
Actually they have three
angles that are equal, but
as soon as you spot two you
know that the third is gonna
match, too.
Congruent shapes are
similar and the same size.
Congruent shapes have
angles that are equal, just
like similar shapes, but
they’re also the same scale.
All squares and
circles are similar.