Geometry Chapter 9 Theorems Flashcards
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Questions and Answers

What is the definition of a reflection in a line?

  • A function that rotates a point about a fixed point.
  • A function that transforms a point without changing its distance.
  • A function that maps a point to its image such that if the point is on the line, then the image and preimage are the same point. (correct)
  • A function that moves a point along a vector.
  • What happens during a reflection in the x-axis?

    Multiply its y-coordinate by -1.

    To reflect a point in the line y=x, interchange the _____ and y-coordinates.

    x

    How do you translate a point in the coordinate plane along vector ⟨a, b⟩?

    <p>Add a to the x-coordinate and b to the y-coordinate.</p> Signup and view all the answers

    What is the definition of a rotation?

    <p>A function that maps a point to its image such that if the point is the center of rotation, then the image and preimage are the same point.</p> Signup and view all the answers

    What is the center of rotation?

    <p>The point around which a rotation occurs.</p> Signup and view all the answers

    What is the angle of rotation?

    <p>The amount of rotation (in degrees) of a figure about a fixed point.</p> Signup and view all the answers

    To rotate a point 90° counterclockwise about the origin, multiply the y-coordinate by -1 and then interchange the ____ and y-coordinates.

    <p>x</p> Signup and view all the answers

    To rotate a point 180° counterclockwise about the origin, multiply the _____ and y-coordinates by -1.

    <p>x</p> Signup and view all the answers

    To rotate a point 270° counterclockwise about the origin, multiply the x-coordinate by -1 and then interchange the ____ and y-coordinates.

    <p>x</p> Signup and view all the answers

    What is a glide reflection?

    <p>The composition of a translation followed by a reflection in a line parallel to the translation vector.</p> Signup and view all the answers

    What is the composition of isometries?

    <p>The composition of two or more isometries.</p> Signup and view all the answers

    Reflections in parallel lines can be described by a translation vector that is perpendicular to the two lines, and ____ the distance between the two lines.

    <p>twice</p> Signup and view all the answers

    Reflections in intersecting lines can be described by a rotation about the point where the lines intersect and through an angle that is _____ the measure of the acute or right angle formed by the lines.

    <p>twice</p> Signup and view all the answers

    If a figure can be mapped onto itself by a reflection in a line, the figure has _________.

    <p>line symmetry</p> Signup and view all the answers

    What is the line of symmetry?

    <p>The line that divides two matching parts.</p> Signup and view all the answers

    If a figure can be mapped onto itself by a rotation between 0° and 360° about the center of the figure, the figure has _________.

    <p>rotational symmetry</p> Signup and view all the answers

    What is the center of symmetry?

    <p>The point about which a rotational symmetry is performed.</p> Signup and view all the answers

    If a figure can be mapped onto itself by a reflection in a plane, the figure has ____________.

    <p>plane symmetry</p> Signup and view all the answers

    If a figure can be mapped onto itself by a rotation between 0° and 360° in a line, the figure has _____________.

    <p>axis symmetry</p> Signup and view all the answers

    Study Notes

    Geometric Transformations

    • Reflections in Intersecting Lines: Composite transformation linked to rotation about the intersection point and twice the acute or right angle formed by the lines.
    • Reflection in a Line: Maps points to their image where the line acts as a perpendicular bisector for points not on the line, ensuring the point on the line remains unchanged.
    • Reflection in the x-axis: Achieved by multiplying the y-coordinate of a point by -1.
    • Reflection in Line y=x: Accomplished by interchanging the x- and y-coordinates of a point.
    • Reflection in the y-axis: Involves multiplying the x-coordinate of a point by -1.

    Translations and Rotations

    • Translation: Maps each point along a given vector, effectively shifting the position of the figure without altering its orientation.
    • Translation in the Coordinate Plane: For a vector ⟨a, b⟩, a point is translated by adding 'a' to the x-coordinate and 'b' to the y-coordinate.
    • Rotation: Centers around a fixed point; if the point coincides with the center, it remains unchanged. Other points maintain a constant distance and specified angle from the center.
    • Angle of Rotation: The degree measurement of the rotation about a fixed point.
    • 90° Rotation in Coordinate Plane: Counterclockwise rotation achieved by multiplying the y-coordinate by -1 and then swapping x and y coordinates.
    • 180° Rotation in Coordinate Plane: Involves multiplying both x and y coordinates by -1.
    • 270° Rotation in Coordinate Plane: Accomplished by multiplying the x-coordinate by -1 first, then swapping x and y coordinates.

    Symmetry

    • Glide Reflection: A combination of translation followed by reflection in a line parallel to the translation vector.
    • Composition of Isometries: Combines two or more isometric transformations that preserve distances and angles.
    • Line Symmetry: Indicates a figure can match itself via a reflection across a specific line.
    • Line of Symmetry: Divides a figure into two mirrored halves; can be vertical, horizontal, or diagonal.
    • Rotational Symmetry: Describes a scenario where a figure maps to itself through rotation anywhere from 0° to 360° about its center.
    • Center of Rotational Symmetry: The point around which a figure rotates symmetrically.
    • Plane Symmetry: Achieved if a figure can reflect itself across a plane.
    • Axis Symmetry: Indicates a figure's ability to map to itself through a rotation along a line.

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    Description

    Explore the key concepts and theorems in Chapter 9 of McGraw Hill Geometry. This quiz includes definitions for important terms like reflections in intersecting lines and translations. Perfect for students looking to reinforce their understanding of geometry concepts through flashcards.

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