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# Topic 3 Vocabulary

### Straughn High School 9th Grade Geomertry

Question | Answer |
---|---|

Composition of rigid motions | a transformation with two or more rigid motions in which the second rigid motion is performed on the image of the first rigid motion |

Image | resulting figure |

Line of reflection | a transformation such that if point A is on line r, then its image B is the point such that line r is the perpendicular bisector of line BB |

Preimage | original figure |

Reflection | a rigid motion that reflects each point in the preimage across a line of reflection |

Transformation | a change in the position, size, or shape of a geometric figure |

Angle of rotation | the positive number of degrees that a figure rotates |

Center of rotation | the point P that an image is rotated around |

Rotation | a rigid motion that rotates each point in the preimage about a point P by an angle measure of x degrees |

Rigid Motion | a transformation that preserves distance and angle measures |

Translation | a transformation that moves points the same distance and in the same direction |

Glide reflection | the composition of a reflection followed by a translation in a direction parallel to the line of reflection |

Line of symmetry | reflection line |

Point symmetry | the type of symmetry for which there is a rotation of 180 degrees that maps a figure onto itself |

Rotational symmetry | the type of symmetry for which there is a rotation of 360 degrees or less that maps a figure onto itself |

Dilation | preserves angle measures ONLY and is a copy of the pre-image that is either larger or smaller than the original. It is NOT one of the rigid motions, but it is a transformation |

Symmetry | a rigid motion that maps the figure onto itself |

Rigid motion | a transformation that preserves distance and angle measure |