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A point specifies only location; it has no length, width, or depth. We usually represent a point with a dot on paper, but the dot we make has some dimension, while a true point has dimension 0.
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A line segment is the portion of a line lying strictly between two points. It has a finite length and no width.
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A ray can be thought of as a half a line. It has a point on one end, and it extends infinitely in the other direction.
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A plane is a flat, two-dimensional object. We often represent a plane by a piece of paper, a blackboard, or the top of a desk. In fact, none of these is actually a plane, because a plane must continue infinitely in all directions and have no thickness at all. A plane can be defined by two intersecting lines or by three non-collinear points.
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lying in the same straight line.
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Two rays with a common endpoint that point in opposite directions and form a straight line.
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In the same plane.
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A shape, formed by two lines or rays diverging from a common point (the vertex)
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A point on a line segment that divides it into two equal parts
The halfway point of a line segment
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A line which cuts an angle into two equal halves
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Two figures are congruent if all corresponding lengths are the same, and if all corresponding angles have the same measure. Colloquially, we say they "are the same size and shape," though they may have different orientation. (One might be rotated or flipped compared to the other.)
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A vertex is the point where two sides of a polygon meet.
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A positive angle that measures less than 90°
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An angle whose measure is greater than 90° and less than 180°
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An angle whose measure is exactly 90°
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An angle whose measure is exactly 180° - a straight line
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Two Angles are Complementary if they add up to 90 degrees (a Right Angle)
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Two angles that add up to 180°
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Vertical Angles are the angles opposite each other when two lines cross.
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Two angles are Adjacent if they have a common side and a common vertex (corner point) and don't overlap.
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Two angles that are adjacent (share a leg) and supplementary (add up to 180°)
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A line is perpendicular to another if it meets or crosses it at right angles (90°).
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A polygon is a two-dimensional geometric figure with these characteristics:
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It is made of straight line segments.
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Each segment touches exactly two other segments, one at each of its endpoints.
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It is closed -- it divides the plane into two distinct regions, one inside and the other outside the polygon.
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A closed figure consisting of three line segments linked end-to-end.
A 3-sided polygon.
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Quadrilateral just means "four sides"
(quad means four, lateral means side).
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A polygon with 5 sides
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A polygon with 6 sides
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A plane figure with eight straight sides and eight angles.
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A plane figure with ten straight sides and angles.
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A plane figure with twelve sides.
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A closed plane figure bounded by three or more line segments.
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Having an outline or surface that curves inward like the interior of a circle or sphere.
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Having an outline or surface curved like the exterior of a circle or sphere.
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| a polygon with all sides and all angles equal |
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A polygon that does not have all sides equal and all angles equal.
A polygon is "regular" only if all angles are equal and all sides are equal otherwise it is irregular.
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(of a straight line) Joining two opposite corners of a square, rectangle, or other straight-sided shape.
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One of the lines that make a flat (2-dimensional) shape.
Or one of the surfaces that make a solid (3-dimensional) object.
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The distance around a two-dimensional shape.
Example: the perimeter of this rectangle is 3+7+3+7 = 20
The perimeter of a circle is called the circumference.
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