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## Unit 5 Vocabulary

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**Point**An exact position or location in a given plane. A point has no dimension; it is represented by a dot. Point A or Point B**Line**A line extends in one dimension. Represented by a straight line with two arrows to indicate that the line extends without end in two directions. There are an infinite number of points that continue beyond these points. Written as**Line Segment**A line segment has two endpoints. Written as**Distance along a line**The linear distance between two points on a given line.**Parallel Line**Lines in a plane that either do not share any points and never intersect, or share all points. Written as**Perpendicular Line**Two lines that intersect at a right angle (90°). Written as**Ray**Part of a line that starts at a point and goes off into one direction infinitely.**Angle**A shape, formed by two lines or rays diverging from a common point (the vertex). The angle is**Right Angle**An angle that measures 90°.**Acute Angle**An angle measuring less than 90° but greater than 0°.**Obtuse Angle**An angle measuring greater than 90° but less than 180°.**Circle**• The set of all points in a plane equidistant from a certain point called the center.**One-to-One**A relationship wherein each point in a set of points is mapped to exactly one other point.**Pre-image**The original figure before undergoing a transformation.**Image**The new, resulting figure after a transformation**Isometry**A transformation in which the preimage and image are congruent.**Transformations are called RIGID if every image is congruent**to its preimage. Rigid transformations can also be referred to as an ISOMETRY. Every segment is congruent to its image.**Which of the following are rigid transformations? (Isometry)****Isometries not onlypreserve lengths, butthey preserve angle**measuresparallel lines, andbetweenness of points**Find the value of each variable, given that the**transformation is an isometry.**Congruent**Figures are congruent if they have the same shape, size, lines, and angles.**Similar Triangles**Triangles are similar if they have the same shape but have different sizes.