Download angle

acute angle
d
An angle that measures less than 90°.
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acute triangle
A triangle in which each of the three angles is acute.
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adjacent angles
a
b
⬔a and ⬔b are adjacent angles.
Angles that share a common side and a
common vertex. Their interiors do not overlap.
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alternate exterior
angles
Transversal
e
g
j
m
f
h
⬔e and ⬔l are alternate exterior angles.
⬔f and ⬔m are alternate exterior angles.
k
l
Exterior angles formed when two lines are
intersected by a transversal.
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alternate interior
angles
Transversal
e
g
j
m
f
h
⬔g and ⬔k are alternate interior angles.
⬔h and ⬔j are alternate interior angles.
k
l
Interior angles formed when two lines are
intersected by a transversal.
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angle
An angle is formed by two rays with a common endpoint.
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angle pairs
Pairs of related angles.
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bisect
To partition a line segment or angle into two congruent parts.
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center
center
A point lying in the middle of a circle that is the same
distance from all points on the circle.
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central angle
central
angle
m
Any angle with a vertex at the center of a circle.
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chord
A
chord
C
A line segment that connects two points on a circle.
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complementary
angles
a
b
⬔a and ⬔b are complementary angles.
Two angles for which the sum of the angle measures is 90°.
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congruent
A
B
D
C
E
F
Figures that have the same size and the same shape.
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corresponding parts
In geometry, matching sides and angles of polygons.
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diagonal
diagonal
A line segment that connects two
vertices of a polygon and is not a side.
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diameter
diameter
A
C
B
Any chord that passes through the center of a circle.
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exterior angle
R
v
S
T
⬔v is an exterior angle of triangle RST.
An angle formed when a side of a polygon is extended.
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interior angle
B
interior angles
A
C
An angle formed by two sides of a polygon.
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interior of an angle
Z
m
Point Z in the interior of ⬔m
The part of the plane between the two rays forming the angle.
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isosceles triangle
A triangle that has two congruent sides.
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line of symmetry
A figure has line symmetry if it can be folded in half and
the two halves are congruent.
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midpoint
midpoint
The point that divides the segment into two congruent parts.
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obtuse angle
An angle with a measure greater than that of a right
angle and less than 180°.
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obtuse triangle
A triangle that has one obtuse angle.
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parallel
Lines or figures that lie in the same plane and do not
intersect. The distance between the lines or figures is
everywhere the same.
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perpendicular
Two lines or line segments that intersect or
meet to form right angles.
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point
An exact location in space, represented by a dot.
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polygon
A simple closed plane figure made up of three
or more line segments.
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radius
A
B
radius
A segment that connects the center of a
circle to any point on the circle.
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reflection
A⬘
A
B⬘
B
A transformation that involves a flipping
movement of a figure over a line.
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regular polygon
A polygon with all sides having the same length
and all angles having the same measure.
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right angle
An angle that measures 90°.
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rotation
A transformation that involves a turning movement
of a figure about a point.
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rotational symmetry
A figure has rotational symmetry if, after the figure is
rotated about a point of less than a full turn, the figure
is the same as when it is in its original position.
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scalene triangle
A triangle whose sides are all different lengths.
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similar
Figures that are the same shape but not
necessarily the same size.
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space
The collection of all points.
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straight angle
An angle whose measure is 180°.
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supplementary angles
s t
⬔s and ⬔t are supplementary angles.
Two angles for which the sum of the angle measures is 180°.
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symmetry
A figure has symmetry when it can be folded
so that both parts match.
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transformation
A geometric change in the position of a figure.
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translation
B⬘
B A⬘
C⬘
A
C
A transformation that involves a sliding
movement of a figure in any direction.
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transversal
transversal
A line intersecting two other lines.
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vertex
vertex
vertex
vertex
A point common to two sides of an angle, polygon, or solid figure.
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vertical angles
c
a
b
d
⬔a and ⬔b are congruent.
⬔c and ⬔d are congruent.
Angles formed by intersecting lines.
Vertical angles are always congruent.
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