Download Marking Period 1 Vocab

acute triangle
a triangle with all acute
angles
adjacent angles
angles that share a
common side and vertex
alternate exterior angles
two non-adjacent exterior
angles on opposite sides of the
transversal; if transversal
intersects parallel lines they are
congruent
alternate interior angles
two non-adjacent interior
angles on opposite sides of the
transversal; if transversal
intersects parallel lines they are
congruent
altitude of a triangle
the perpendicular segment
from a vertex of a triangle to
the opposite side or to the
line that contains the
opposite side
angle
a figure formed by two
rays with a common
endpoint called the vertex
central angle
of a regular polygon is an
angle formed by radii
drawn to two consecutive
vertices
circumcenter of a triangle
the point of concurrency
of the perpendicular
bisectors of the three
sides of a triangle
collinear
points that lie on the
same line
complementary angles
two angles whose
measures have a sum of
90 degrees
compositions of
transformations
multiple transformations
performed on an image
concurrent
a point where three or
more lines intersect at
one point
congruent
having the same size and
shape
construction
a geometric drawing
created using only a
compass and a straight
edge
coplanar
points and lines that lie in
the same plane
corresponding angles
lie on the same side of the
transversal and in
corresponding positions; if
transversal intersects parallel
lines they are congruent
dilation
a transformation that
changes the size of an
object, but not the shape;
not an isometry
directed line segment
a line segments named by
its starting point and
ending point
equal
having the same
numerical value
equidistant
same distance from a
point of line as another
point or line.
equilateral triangle
has three equal sides,
each of the angles
measures 60°
exterior angle
an angle outside the
polygon formed by a side
and an extension of an
adjacent side
image
the figure you get after a
transformation
incenter
the point of concurrency
of the three angle
bisectors of a triangle
interior angle
formed by two sides of a
polygon, the sum of the angles
in degrees of any polygon is
180(n-2) where n is the
number of sides
isometry
transformation that
preserves lengths, angle
measures, parallel lines,
and distances between
points
isosceles triangle
a triangle in which at least
two sides have the same
length
line
a straight object that is infinitely
long and infinitely thin; a straight
path that extends without end in
opposite directions; in coordinate
geometry y = mx + b
linear pair
two angles that are
adjacent to each other
and are supplementary
line segment
two points and all of the
points on the line
connecting them, named
by its two endpoints
mapping of a transformation
the pairing of every point
in a preimage with a point
in an image
median of a triangle
segment from a vertex to
the midpoint of the
opposite side
midpoint
the point that is halfway
between the endpoints of
the line segment
obtuse triangle
a triangle with one obtuse
angle
opposite ray
two rays that have a
common endpoint and
form a line
parallel
two lines that are in the
same plane, but do not
intersect
parallel lines
two lines that are in the
same plane, but do not
intersect, have the same
slope
perpendicular
lines that intersect at
right angles
perpendicular bisector
a ray, line, segment, or
plane that is
perpendicular to a
segment at its midpoint
plane
a flat surface that extends
without end in all directions;
infinite number of connected
lines in a flat surface; 2D
point
a specific location in
space that has no size or
shape; named with a
capital letter
polygon
a closed plane figure
formed by three or more
line segments
preimage
in a transformation, it is
the original figure.
radius
a segment whose
endpoints are the center
and any point on the
circle.
ray
a portion of a line that
begins at one endpoint
and extends without end
in one direction only
reflection
an isometry that flips the
figure over a line
right triangle
a triangle with one right
angle
rigid motion
preserves distance and
angle measures
rotation
an isometry that turns a
figure about a fixed point
scalene triangle
a triangle with no
congruent sides
segment bisector
a ray, line, segment, or
plane that divides a
segment into two parts of
equal measure
similarity
two polygons are similar if and
only if their corresponding
angles are equal and their
corresponding sides are
proportional.
skew
lines that do not intersect
and are not coplanar
supplementary angles
two angles whose
measures have a sum of
180 degrees
transformation
the moving of a figure by
a translation (slide),
rotation (turn) or
reflection (flip)
translation
an isometry that "slides"
each point of a figure the
same distance in the
same direction; (x+a,
y+b)
transversal
a line that intersects two
coplanar lines
triangle
consists of three straight
side whose three angles
always add up to 180°
triangle inequality theorem
the sum of the lengths of
ANY two sides of a
triangle must be greater
than the length of the
third side
vertical angles
angles that are formed by
two intersecting lines but
are NOT adjacent;
measures are congruent