# Geometry Ch. 9 - Transformations

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Vocab and other stuff from Ch. 9

### isometry

a transformation in which the preimage and image are congruent

### reflection

a transformation representing a flip of the figure over a point, line, or plane

### (a, -b)

the image of (a, b) reflected over the x-axis

### (-a, b)

the image of (a, b) reflected over the y-axis

### (-a, -b)

the image of (a, b) reflected through the origin

### (b, a)

the image of (a, b) reflected over the line y = x

### translation

a transformation that moves all points of a figure the same distance in the same direction

### composition

a transformation made up of successive transformations

### rotation

a transformation that turns every point of a preimage through a specified angle and direction about a fixed point

### angle of rotation

the angle through which a preimage is rotated to form the image

### rotational symmetry

If a figure can be rotated less that 360° about a point so that the image and the preimage are indistinguishable, then the figure has ___

### order

# of rotations less than 360° that produce an image indistinguishable from the original

### magnitude

360° divided by the order

### tessellation

a pattern that covers a plane by transforming the same figure or set of figures so that there are no overlapping or empty spaces

### regular

if a tessellation is formed by only one type of regular polygon, then the tessellation is ___

### semi-regular

if a uniform tessellation is formed by more than one type of regular polygon, then the tessellation is ___

### uniform

a tessellation that has the same arrangement of shapes and angles at each vertex is called ___

### dilation

a transformation that enlarges or reduces a figure

### enlargement

if |r| > 1, the dilation is a(n) ___

### reduction

if 0 > |r| > 1, the dilation is a(n) ___

### congruence transformation

if |r| = 1, the dilation is a(n) ___

### (rx, ry)

if (x, y) is the preimage of a dilation centered at the origin with scale factor r, then the image is ___

Example: