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Acute Triangle

A triangle with three acute angles

Acute Angle

an angle that measures less than 90 degrees

Angle

two rays with a common endpoint, called the vertex

center of rotation

the fixed point a figure is rotated on during a rotation

collinear

points that lie on the same line

complementary angles

Two angles whose sum is 90 degrees

Congruent angles

Angles that have the same measure

congruent figures

figures that have the same size and shape

congruent segments

Segments that have the same length

degrees

a unit for measuring angles

equilateral triangle

A triangle with 3 congruent sides

exterior angles

angles on the outside of parallel lines when cut by a transversal

image

result of a transformation of a point,line or plane

interior angles

angles on the inside of the parallel lines when cut by a transversal

intersecting lines

two lines that share exactly one point

isosceles triangle

A triangle with at least two congruent sides

line

a series of points that extends in opposite directions without end

line of reflection

The line over which a figure is reflected.

line of symmetry

A line that divides a figure into two halves that are mirror images of each other.

line symmetry

if you can draw a line throughit so that the 2 sides are mirror images of each other

obtuse angle

An angle that measures more than 90 degrees but less than 180 degrees

obtuse triangle

a triangle with one obtuse angle

parallel lines

lines in the same plane that never intersect

parallelogram

A quadrilateral with both pairs of opposite sides parallel

perpendicular lines

Lines that intersect to form right angles

plane

A flat surface that extends without end in all directions

point

a location in space that has no size

polygon

Three or more line segments in a plane that forms a closed figure. The line segments never cross but meet at their endpoints.

quadrilateral

A polygon with four sides

ray

a part of a line that begins at a point and continues without end in one direction

rectangle

a parallelogram with four right angles

reflection

A transformation that "flips" a figure over a mirror or reflection line.

rhombus

a parallelogram with four congruent sides

right angle

an angle that measures 90 degrees

right triangle

a triangle with one right angle

rotation

A transformation that turns a figure about a fixed point at a given angle and a given direction.

scalene triangle

a triangle with no congruent sides

segment

part of a line with two end points

similar figures

Figures that have the same shape but different sizes; their sides are proportional, while their corresponding angles are equal

skew lines

lines that lie in different planes. they are neither parallel or intersecting

square

A parallelogram with four congruent sides and four right angles

straight angle

an angle that measures 180 degrees

supplementary angles

two angles whose measures have a sum of 180 degrees

translation

A transformation that "slides" each point of a figure the same distance in the same direction.

transversal

A line that intersects two or more lines.

trapezoid

a quadrilateral with exactly one pair of parallel sides

vertex

the point of intersection of the two rays that form the sides of the angle

vertical angles

angles formed by two intersecting lines. Vertical angles are equal