Unit 1 Transformations Vocabulary

translation

A movement (slide) of a figure along a straight line.

rotational symmetry

A shape has Rotational Symmetry when it still looks the same after a rotation (of less than one full turn).

Horizontal translation

A slide to the right or left; the x-coordinate changes.

reflection

A transformation that "flips" a figure over a mirror or reflection line.

rotation

A transformation that "turns" a figure about a fixed point at a given angle and a given direction.

dilation

A transformation that changes the size of an object, but not the shape.

non-isometric transformation

A transformation that changes the size of the shape. A dilation is an example.

Vertical translation

An up or down slide; the y-coordinate changes.

counter-clockwise

In the direction opposite to the rotation of the hands of a clock.

triangle A'B'C'

Method of labeling a triangle that results from a transformation. Read as triangle A prime, B prime, C prime.

reflection across the x-axis

Quadrilateral A'B'C'D' is the new (reflected) image.

90 degree rotation clockwise

Quadrilateral A'B'C'D' is the new (rotated) image. (x,y) ---> (y,-x)

image

The figure that results from a transformation.

pre-image

The original figure in a transformation.

scale factor

This shows how much bigger or smaller a shape is after a dilation. The variable k is used for this.

transformation

To change the properties of a shape.

reflection across the y-axis

Triangle A'B'C' is the new (reflected) image.

180 degree rotation

Triangle A'B'C' is the new (rotated) image. (x,y) ---> (-y,-x)

90 degree rotation counter - clockwise

Triangle A'B'C' is the new (rotated) image. (x,y) ---> (-y,x)

clockwise

in the same direction as the rotating hands of a clock

reflection symmetry

sometimes called Line Symmetry or Mirror Symmetry) is easy to see, because one half is the reflection of the other half.

rigid motion/isometry

the type of transformation that results in two shapes that are an congruent.