Download U3 study guide geometry terms

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Study guide - unit 3 - Geometry Terms
Unit 3
Term
Definition
Polygon
A closed figure
with three or more
straight sides. We
name a polygon by
the number of its
sides. For example,
a five-sided
polygon is a
pentagon
equilateral
triangle
A triangle with
all sides equal
isosceles
triangle
A triangle with
two sides equal
scalene
triangle
A triangle with
no sides equal
acute angle
An angle that
measures less than
90°
Acute  cute =
small
Acutus is latin for
sharp, pointed
right angle
Angulus is Latin
for corner
A right angle
measures 90°.
Two lines that
meet in a square
corner make a
Example
right angle.
obtuse angle
An angle
measuring
between 90° and
180°.
Obtuse === obese
Obtusus = Latin for
blunt
perpendicular Two lines that
intersect at a right
angle are
perpendicular.
acute triangle
A triangle with all
angles less than
90°.
right triangle
A triangle with one
90° angle.
obtuse
triangle
A triangle with one
angle greater than
90° and less than
180°.
regular
polygon
A regular polygon
has all sides equal
and all angles
equal.
irregular
polygon
A polygon that
does not have all
sides equal or all
angles equal.
net
An arrangement
that shows all the
faces of a solid,
joined in one
piece. It can be
folded to form the
solid.
Quadrilateral
A figure with 4
sides.
pentagon
A polygon with 5
sides.
Pente is a Greek word
that means five, 5
Gonia is Greek for
corner, angle.
hexagon
A polygon with 6
sides.
Hexa is Greek for 6.
octagon
A polygon with 8
sides.
Octagonon is Greek
for 8 angles
prism
A solid with 2
bases.
pyramid
A solid with one
base.
protractor
An instrument that
measures the
number of degrees
in an angle.
Reflex Angle
An angle between
180° and 360°