CHAPTER
1
Geometry Flashcards
A figure formed by two rays with a
common endpoint.
Chapter 1 (p. 20, 1-3)
angle
∠A
The number of nonoverlapping unit
squares of a given size that will exactly
cover the interior of a plane figure.
Chapter 1 (p. 36, 1-5)
area
The area is 10 square units.
A plane that is divided into four regions
by a horizontal line called the x-axis and a
vertical line called the y-axis.
Chapter 1 (p. 43, 1-6)
YAXIS
coordinate plane
XAXIS
An undefined term in geometry, a line is
a straight path that has no thickness and
extends forever.
Chapter 1 (p. 6, 1-1)
line
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CHAPTER
1
Geometry Flashcards
The sum of the side lengths of a closed
plane figure.
Chapter 1 (p. 36, 1-5)
FT
perimeter
FT
Perimeter = 18 + 6 + 18 + 6 = 48 ft
An undefined term in geometry, it is a flat
surface that has no thickness and extends
forever.
Chapter 1 (p. 6, 1-1)
!
plane
#
"
plane R or plane ABC
An undefined term in geometry, it names a
location and has no size.
Chapter 1 (p. 6, 1-1)
0
point
point P
A change in the position, size, or shape of
a figure or graph.
Chapter 1 (p. 50, 1-7)
"
"Ī
0REIMAGE
transformation
!
)MAGE
#
!Ī
̱!"#̱!Ī"Ī#Ī
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CHAPTER
2
Geometry Flashcards
A statement that is believed to be true.
Chapter 2 (p. 74, 2-1)
A sequence begins with the
terms 2, 4, 6, 8, 10. A reasonable
conjecture is that the next term
in the sequence is 12.
conjecture
An example that proves that a conjecture
or statement is false.
Chapter 2 (p. 75, 2-1)
counterexample
The process of using logic to draw
conclusions.
Chapter 2 (p. 88, 2-3)
deductive reasoning
The process of reasoning that a rule or
statement is true because specific cases
are true.
Chapter 2 (p. 74, 2-1)
inductive reasoning
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CHAPTER
2
Geometry Flashcards
A closed plane figure formed by three or
more segments such that each segment
intersects exactly two other segments
only at their endpoints and no two
segments with a common endpoint are
collinear.
Chapter 2 (p. 98, 2-4)
polygon
An argument that uses logic to show that
a conclusion is true.
Chapter 2 (p. 104, 2-5)
proof
A four-sided polygon.
Chapter 2 (p. 98, 2-4)
quadrilateral
A statement that has been proven.
Chapter 2 (p. 110, 2-6)
theorem
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CHAPTER
3
Geometry Flashcards
For two lines intersected by a transversal,
a pair of angles that lie on opposite sides
of the transversal and outside the other
two lines.
Chapter 3 (p. 147, 3-1)
£ Ó
x È
alternate exterior
angles
Î {
Ç n
∠4 and ∠5 are alternate
interior angles.
For two lines intersected by a transversal,
a pair of nonadjacent angles that lie on
opposite sides of the transversal and
between the other two lines.
Chapter 3 (p. 147, 3-1)
£ Ó
x È
alternate interior
angles
Î {
Ç n
∠3 and ∠6 are alternate
interior angles.
For two lines intersected by a transversal,
a pair of angles that lie on the same side
of the transversal and on the same sides
of the other two lines.
Chapter 3 (p. 147, 3-1)
corresponding angles
£ Ó
x È
Î {
Ç n
∠1 and ∠3 are corresponding.
A line perpendicular to a segment at the
segment’s midpoint.
Chapter 3 (p. 172, 3-4)
Ű
perpendicular bisector
!
"
is the perpendicular bisector
_
of AB .
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CHAPTER
3
Geometry Flashcards
Lines that intersect at 90° angles.
Chapter 3 (p. 146, 3-1)
N
M
perpendicular lines
m⊥n
For two lines intersected by a transversal,
a pair of angles that lie on the same side
of the transversal and between the
two lines.
Chapter 3 (p. 147, 3-1)
£ Ó
x È
same-side interior
angles
Î {
Ç n
∠2 and ∠3 are same-side
interior angles.
A measure of the steepness of a line. If
(x 1, y 1) and (x 2, y 2) are any two points on
the line, the slope of the line, known as m,
y -y
is represented by the equation m = ______
x -x
.
Chapter 3 (p. 182, 3-5)
2
1
2
1
slope
A line that intersects two coplanar lines at
two different points.
Chapter 3 (p. 147, 3-1)
£ Ó
x È
transversal
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Î {
Ç n
/À>˜ÃÛiÀÃ>
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CHAPTER
4
Geometry Flashcards
Chapter 4 (p. 216, 4-1)
A triangle with three acute angles. An
acute angle measures less than 90°.
acute triangle
Whose corresponding sides and angles
are congruent.
Chapter 4 (p. 231, 4-3)
congruent polygons
Chapter 4 (p. 217, 4-1)
A triangle with three congruent
sides.
equilateral triangle
An angle formed by one side of a
polygon and the extension of an
adjacent side.
Chapter 4 (p. 225, 4-2)
exterior angle of a
polygon
2
1
3
4
5
∠5 is an exterior angle
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CHAPTER
4
Geometry Flashcards
Chapter 4 (p. 217, 4-1)
A triangle with at least two congruent
sides.
isosceles triangle
Chapter 4 (p. 216, 4-1)
A triangle with one obtuse angle. An
obtuse angle measures more than 90°.
obtuse triangle
Chapter 4 (p. 216, 4-1)
A triangle with one right angle.
right triangle
A triangle with no congruent sides.
Chapter 4 (p. 217, 4-1)
scalene triangle
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CHAPTER
5
Geometry Flashcards
A perpendicular segment from a vertex to
the line containing the opposite side.
Chapter 5 (p. 316, 5-3)
altitude of a triangle
H
The point of concurrency of the three
medians of a triangle. Also known as the
center of gravity.
Chapter 5 (p. 314, 5-3)
"
centroid of a triangle
8
!
0
9
#
:
The centroid is P.
The point of concurrency of the three
perpendicular bisectors of a triangle.
Chapter 5 (p. 307, 5-2)
"
circumcenter
of a triangle
0
!
#
The circumcenter is P.
Three or more lines that intersect at one
point.
Chapter 5 (p. 307, 5-2)
concurrent
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CHAPTER
5
Geometry Flashcards
The point of concurrency of the three
angle bisectors of a triangle.
Chapter 5 (p. 309, 5-2)
G
P is the incenter.
K
incenter of a triangle
M
H
P
L
J
A segment whose endpoints are a vertex
of the triangle and the midpoint of the
opposite side.
Chapter 5 (p. 314, 5-3)
#
median of a triangle
-EDIAN
!
"
$
A segment that joins the midpoints of two
sides of the triangle.
Chapter 5 (p. 322, 5-4)
"
$
midsegment of a
triangle
!
%
#
The point of concurrency of the three
altitudes of a triangle.
Chapter 5 (p. 316, 5-3)
P is the orthocenter.
orthocenter of a
triangle
0
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CHAPTER
6
Geometry Flashcards
A polygon in which a diagonal can be
drawn such that part of the diagonal
contains points in the exterior of the
polygon.
Chapter 6 (p. 383, 6-1)
concave polygon
œ˜V>Ûi
µÕ>`Àˆ>ÌiÀ>
A segment connecting two
nonconsecutive vertices of a polygon.
Chapter 6 (p. 382, 6-1)
"
!
#
diagonal of a polygon
%
$IAGONAL
$
A trapezoid in which the legs are
congruent.
Chapter 6 (p. 429, 6-6)
"
#
isosceles trapezoid
!
$
A quadrilateral with exactly two pairs of
congruent consecutive sides.
Chapter 6 (p. 427, 6-6)
"
!
kite
#
$
+ITE!"#$
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CHAPTER
6
Geometry Flashcards
A quadrilateral with four right angles.
Chapter 6 (p. 408, 6-4)
rectangle
A polygon that is both equilateral and
equiangular.
Chapter 6 (p. 382, 6-1)
regular polygon
A quadrilateral with four congruent sides.
Chapter 6 (p. 409, 6-4)
rhombus
A quadrilateral with exactly one pair of
parallel sides.
Chapter 6 (p. 429, 6-6)
"
#
trapezoid
!
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$
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CHAPTER
7
Geometry Flashcards
A transformation in which the lines
connecting every point P with its preimage P
all intersect at a point C known as the center
___ is the same for every point
of dilation, and CP
CP
P; a transformation that changes the size of a
figure but not its shape.
Chapter 7 (p. 495, 7-6)
dilation
$@
$
%
#
%@
&
&@
A statement that two ratios are equal;
a
c
__
= __
.
b
d
Chapter 7 (p. 455, 7-1)
2 =_
4
_
3
6
proportion
A drawing that uses a scale to represent
an object as smaller or larger than the
actual object.
Chapter 7 (p. 489, 7-5)
scale drawing
A blueprint is an example
of a scale drawing.
The multiplier used on each dimension to
change one figure into a similar figure.
Chapter 7 (p. 495, 7-6)
Y
!Ī
scale factor
!
"Ī
"
X
#
#Ī
Scale factor: 2
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CHAPTER
7
Geometry Flashcards
Two figures are similar if they have the
same shape but not necessarily the same
size.
Chapter 7 (p. 462, 7-2)
similar
Two polygons whose corresponding
angles are congruent and whose
corresponding sides are proportional.
Chapter 7 (p. 462, 7-2)
*
similar polygons
0
,
. 3
3.5 = _
5
Similarity ratio: _
3
2.1
similarity ratio
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The ratio of two corresponding linear
measurements in a pair of similar figures.
Chapter 7 (p. 463, 7-2)
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Holt Geometry
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CHAPTER
8
Geometry Flashcards
The angle formed by a horizontal line
and a line of sight to a point below.
Chapter 8 (p. 544, 8-4)
angle of depression
The angle formed by a horizontal line
and a line of sight to a point above.
Chapter 8 (p. 544, 8-4)
angle of elevation
In a right triangle, the cosine of angle
A is the ratio of the length of the leg
adjacent to angle A to the length of the
hypotenuse. It is the reciprocal of the
secant function.
Chapter 8 (p. 525, 8-4)
HYPOTENUSE
cosine
!
ADJACENT
adjacent
1
cos A = __= _
sec A
hypotenuse
For postive numbers a and b, the postive
a = __
x . In a geometric
number x such that __
x
b
sequence, a term that comes beween
two given nonconsecutive terms of the
sequence.
Chapter 8 (p. 519, 8-1)
geometric mean
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a =_
x
_
x
b
x 2 = ab
ab
x = √
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CHAPTER
8
Geometry Flashcards
In a right triangle, the ratio of the length
of the leg opposite ∠A to the length of the
hypotenuse.
Chapter 8 (p. 525, 8-2)
HYPOTENUSE
OPPOSITE
sine
!
opposite
sin A = __
hypotenuse
In a right triangle, the ratio of the length
of the leg opposite ∠A to the length of the
leg adjacent to ∠A.
Chapter 8 (p. 525, 8-2)
OPPOSITE
tangent of an angle
!
ADJACENT
opposite
tan A = _
adjacent
A ratio of two sides of a right triangle.
Chapter 8 (p. 525, 8-2)
"
C
trigonometric ratio
!
B
A
#
a ; cos A = _
b ; tan A = _
a
sin A = _
c
c
b
A quantity that has both magnitude and
direction.
Chapter 8 (p. 559, 8-6)
Ч
U
vector
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CHAPTER
9
Geometry Flashcards
The perpendicular distance from the
center of a regular polygon to a side of
the polygon.
Chapter 9 (p. 601, 9-2)
apothem
A
The point inside a circle that is the same
distance from every point on the circle.
Chapter 9 (p. 600, 9-2)
center of a circle
!
The point that is equidistant from all
vertices of the regular polygon.
Chapter 9 (p. 601, 9-2)
center of a
regular polygon
An angle whose vertex is the center of the
regular polygon and whose sides pass
through consecutive vertices.
Chapter 9 (p. 601, 9-2)
center angle of a
regular polygon
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i˜ÌÀ>Ê
>˜}i
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CHAPTER
9
Geometry Flashcards
The set of points in a plane that are a
fixed distance from a given point called
the center of the circle.
Chapter 9 (p. 600, 9-2)
circle
A plane figure that can be divided
into other simple shapes, or a threedimensional figure that can be divided
into other simple three-dimensional
figures.
Chapter 9 (p. 606, 9-3)
composite figure
A form of theoretical probability determined
by a ratio of geometric measures such as
lengths, areas, or volumes.
Chapter 9 (p. 630, 9-6)
yellow
geometric probability
ƒ
ƒ
purple
ƒ
ƒ
red
green
ƒ
blue
The probability of the
2
pointer landing on red is __
.
9
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CHAPTER
10
Geometry Flashcards
A three-dimensional figure with a circular
base and a curved lateral surface that
connects the base to a point called the
vertex.
Chapter 10 (p. 654, 10-1)
cone
A three-dimensional figure with two
parallel circular bases and connected by a
curved lateral surface.
Chapter 10 (p. 654, 10-1)
cylinder
A diagram of the faces of a three-dimensional
figure arranged in such a way that the
diagram can be folded to form the figure.
Chapter 10 (p. 655, 10-1)
net
M
M
M
M
A polyhedron formed by two parallel
congruent polygonal bases connected by
lateral faces that are parallelograms.
Chapter 10 (p. 654, 10-1)
prism
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CHAPTER
10
Geometry Flashcards
A polyhedron formed by a polygonal base
and triangular lateral faces that meet at a
common vertex.
Chapter 10 (p. 654, 10-1)
pyramid
The set of points in space that are a fixed
distance from a given point called the
center of the sphere.
Chapter 10 (p. 714, 10-8)
sphere
The total area of all faces and curved
surfaces of a three-dimensional figure.
Chapter 10 (p. 680, 10-4)
CM
surface area
CM
CM
Surface area = 2(8)(12) + 2(8)(6) +
2
2(12)(6) = 432 cm
The number of nonoverlapping unit cubes
of a given size that will exactly fill the
interior of a three-dimensional figure.
Chapter 10 (p. 697, 10-6)
FT
volume
FT
FT
3
Volume = (3)(4)(12) = 144 ft
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CHAPTER
11
Geometry Flashcards
An unbroken part of a circle consisting
of two points on the circle, called the
endponts, and all the points on the circle
between them.
Chapter 11 (p. 756, 11-2)
2
arc
3
The distance along an arc measured in
linear units.
Chapter 11 (p. 766, 11-3)
FT
$
arc length
= 5π ft
mCD
#
ƒ
An angle whose vertex is the center of a
circle.
Chapter 11 (p. 756, 11-2)
central angle of
a circle
A line that intersects a circle at two
points.
Chapter 11 (p. 746, 11-1)
Ű
3ECANT
secant of a circle
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CHAPTER
11
Geometry Flashcards
A region inside a circle bounded by two
radii of the circle and their intercepted arc.
Chapter 11 (p. 764, 11-3)
!
sector of a circle
#
"
A region inside a circle bounded by a
chord and an arc.
Chapter 11 (p. 765, 11-3)
2
segment of a circle
0
1
An arc of a circle whose endpoints lie on
a diameter.
Chapter 11 (p. 746, 11-2)
semicircle
%
'
A line that is in the same plane as a circle
and intersects the circle at exactly one
point.
Chapter 11 (p. 746, 11-1)
"
Ű
tangent of a circle
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CHAPTER
12
Geometry Flashcards
One transformation followed by another
transformation.
Chapter 12 (p. 848, 12-4)
.ĪĪ
0ĪĪ
-ĪĪ
composition of
transformations
Ű
-Ī
.
VЬ
0
.Ī
0Ī
A composition of a translation and a
reflection across a line parallel to the
translation vector.
Chapter 12 (p. 848, 12-4)
VЬ
&IRSTTRANSLATETHE
PREIMAGEALONGY
Ь
*
glide reflection
+
,
Ű
+Ī
*Ī
,Ī
4HENREFLECTTHE
IMAGEACROSSLINEŰ
A transformation that does not change the
size or shape of a figure.
Chapter 12 (p. 824, 12-1)
Reflections, translations, and
rotations are all examples of
isometries.
isometry
In the transformation of a figure such that
the image coincides with the preimage,
the image and preimage have symmetry.
Chapter 12 (p. 856, 12-5)
symmetry
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CHAPTER
12
Geometry Flashcards
A repeating pattern of plane figures that
completely covers a plane with no gaps or
overlaps.
Chapter 12 (p. 863, 12-6)
tessellation
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