Term | Definition |
Undefined Term | A word that does not have a formal definition but there is agreement about what the word means. |
Point | A point has no dimension. It is usually represented by a dot. |
Line | A line has one dimension. It is usually represented by a straight line with two arrowheads to indicated that the line extends without end in two directions. |
Plane | A plane has two dimensions. It is usually represented by a shape that looks a floor or a wall. You must imagine that the plane extends without end, even though the drawing of a plane appears to have edges. |
Collinear points | Point that lie on the same line. |
Coplanar points | Points that lie on the same plane. |
Defined terms | Terms that can be described using known words. |
Line segment | Part of a line that consists of two points. called endpoints , and all points on line that are between the endpoints. Also called segment. |
Endpoints | Part of a line that consists of two points, called endpoints. |
Ray | Part of a line that consists of a point called an endpoint and all points on the that extend in one direction. |
Opposite Rays | If point C lies on line AB between A and B then line CA and line CB are opposite rays. |
Intersection | The set of points that two or more geometric figures have in common |
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Postulate | A rule that is accepted without proof. Also called axioma |
Coordinate of a point | The real number that corresponds to a point on a line. |
Distance between points | The absolute value of the different of the coordinates of the points. The distances between points A and B written as AB, is also called the length of line AB. |
Ruler Postulate | A rule that is accepted without proof. |
Segment Addition Postulate | It says that if B is between A and C, then AB + BC = AC. The converse is also the same. If AB + BC = AC, then B is between A and C. The segment addition postulate is used often in proofs involving the congruence of segments. |
Congruent segment | Line segments that have the same length. |
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Midpoint | A point that divides , or bisects, a segment into two congruent segments. |
Segment bisector | A point,ray,line,segment,or plane that intersect a segment at its midpoint. |
Distance formula | D equals the square roots of (X2-X1)squared plus (Y2-Y1)squared. |
Midpoint formula | You take the two numbers and you add them together and then divide their sum by 2. |