Terms for the Algebra/Geometry Midterm

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Plane

A flat surface extending in 2 directions without end (name using 3 NON-colinear points)

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Space

The set of all points

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Line

Points extending in opposite directions without end

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Segment

A portion of a line between 2 end points

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Ray

A portion of a line with 1 endpoint that extends in 1 direction to infinity

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Angle

The intersection of 2 rays

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Acute angle

An angle whose measure is less than 90 degrees

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Right angle

An angle whose measure equals 90 degrees

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Obtuse angle

An angle whose measure is between 90 and 180 degrees

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Straight angle

An angle whose measure equals 180 degrees

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Collinear

Means points on the same line

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Complementary angles

Two angles whose sum is 90 degrees

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Supplementary angles

Two angles, of whose sum is 180 degrees

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Coplanar

Points in the same plane

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Rectangle

a parallelogram with all four sides forming right angles

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Midpoint

Point in the middle of a segment

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Opposite rays

Rays that are going in opposite directions and share the endpoint

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Parallel

Lines in the plane that do not intersect.

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Perpendicular

Lines that intersect forming right angles

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Skew lines

Lines that are in different planes that do not intersect

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Acute triangle

A triangle in which all the angles are less than 90 degrees

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Scalene triangle

A triangle with none of the sides being congruent

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Isosceles triangle

A triangle with at least 2 that are congruent

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Equilateral triangle

A triangle with equal sides

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Circle

The set of all points in a plain equal distance from a center point

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Regular polygon

A polygon with all the angles and sides being congruent

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Major arch

An arch whose measure is more than 180 degrees

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Semicircle

An arch whose measure equals 180 degrees

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Parallelogram

A quadrilateral whose opposite sides are both parallel

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Rhombus

A parallelogram with all 4 sides being congruent and forming right angles

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Trapezoid

A quadrilateral with 1 pair of opposite sides being parallel

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Similar

When a figure is an enlargement or reduction of a original figure

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Isometry

When the pre-image and the final image are congruent

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Dilation

A similarity transformation (can be a enlargement or a reduction)

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Translation

The "shift" of a figure over parallel lines of reflection (orientation is the same)

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Rotation

The reflection of a figure over 2 intersecting lines (orientation is the same)

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Glide Reflection

The reflection of a figure over at least 3 intersecting lines

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Tessellation

A repeated geometric pattern that covers a plane