Basic Transformations in Geometry

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Describe the composition of transformation: First, the triangle was reflected over the x-axis, then translated horizontally 6 units to the right and vertically 2 units up.

First reflect over the x-axis, then translate right 6 units and up 2 units.

Describe the composition of transformations: First the triangle was rotated 180° about the origin, then reflected over the x-axis.

Rotate 180° about the origin, then reflect over the x-axis.

These are examples of _________.

Non-rigid transformations

These are examples of _________.

<p>Rigid transformations</p> Signup and view all the answers

State the rule for the transformation: first (x,y)→(x,-y), then (x,y)→(x-5,y).

<p>Reflect over the x-axis then translate left 5 units.</p> Signup and view all the answers

State the rule for the transformation: first (x,y)→(x+10,y), then (x,y)→(x,-y).

<p>Translate right 10 units then reflect over the x-axis.</p> Signup and view all the answers

State the rule for the transformation: first (x,y)→(x+1,y-3), then (x,y)→(-x,y).

<p>Translate right 1 unit and down 3 units, then reflect over the y-axis.</p> Signup and view all the answers

State the rule for the transformation: (x,y)→(-x,-y).

<p>Reflect over both axes.</p> Signup and view all the answers

State the rule for the transformation: first (x,y)→(-x,y), then (x,y)→(x,y-4).

<p>Reflect over the y-axis then translate down 4 units.</p> Signup and view all the answers

State the rule for the transformation: first (x,y)→(x,y+4), then (x,y)→(-x,y).

<p>Translate up 4 units then reflect over the y-axis.</p> Signup and view all the answers

Describe the composition of transformations: First the triangle was rotated 180° about the origin, then reflected over the y-axis.

<p>Rotate 180° about the origin then reflect over the y-axis.</p> Signup and view all the answers

Mirror image over a given line is known as __________.

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

Moving a shape about a fixed point (the origin is point (0,0)) is called __________.

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

Sliding all the points of a shape according to given directions (up/down changing y, right/left changing x) is known as __________.

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

The small hash mark that you put next to the point labels of the image (ie: A') is called __________.

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

To reflect a point over the x-axis, the transformation is expressed as __________.

<p>(x,y)→(x,-y)</p> Signup and view all the answers

To reflect a point over the y-axis, the transformation is expressed as __________.

<p>(x,y)→(-x,y)</p> Signup and view all the answers

To reflect a point over the line y=x, the transformation is expressed as __________.

<p>(x,y)→(y,x)</p> Signup and view all the answers

To reflect a point over the line y=-x, the transformation is expressed as __________.

<p>(x,y)→(-y,-x)</p> Signup and view all the answers

To rotate a point about the origin (point (0,0)) 90° Clockwise, the transformation is expressed as __________.

<p>(x,y)→(y,-x)</p> Signup and view all the answers

To rotate a point about the origin (point (0,0)) 180° Clockwise, the transformation is expressed as __________.

<p>(x,y)→(-x,-y)</p> Signup and view all the answers

To rotate a point about the origin (point (0,0)) 90° Counter-Clockwise, the transformation is expressed as __________.

<p>(x,y)→(-y,x)</p> Signup and view all the answers

To rotate a point about the origin (point (0,0)) 360° Clockwise, the transformation is expressed as __________.

<p>(x,y)→(x,y)</p> Signup and view all the answers

If you compose two reflections over parallel lines that are h units apart, it is equivalent to a single translation of __________.

<p>2h units</p> Signup and view all the answers

If you compose two reflections, one over each axis, the final image is a rotation of __________ of the original about the origin.

<p>180°</p> Signup and view all the answers

If you compose two reflections over lines that intersect at x, the resulting image is a rotation of __________.

<p>2x</p> Signup and view all the answers

A composition of a reflection and a translation is known as __________.

<p>Glide reflection</p> Signup and view all the answers

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Study Notes

Compositions of Transformations

  • Compositions involve performing multiple transformations in sequence on a geometric figure.
  • Example: A triangle can first be reflected over the x-axis, then translated right 6 units and up 2 units.

Basic Transformations

  • Reflection: Creates a mirror image across a specified line.
  • Rotation: Moves a shape around a fixed point (often the origin).
  • Translation: Shifts all points of a shape according to specified directions (changes in x and y coordinates).

Rigid vs. Non-Rigid Transformations

  • Rigid Transformations: Preserve size and shape (e.g., rotations, reflections).
  • Non-Rigid Transformations: Do not preserve size and shape (e.g., dilations).

Transformation Rules

  • Reflect over the x-axis: (x,y) → (x, -y)
  • Translate horizontally and vertically: applied sequentially, e.g., first (x,y) → (x+10,y) then apply another transformation.
  • Composite transformation example: First (x,y) → (x+1,y-3) then apply reflection as (-x,y) resulting in the final position.

Specific Transformation Rules

  • To reflect over the y-axis: (x,y) → (-x, y)
  • To reflect over the line y=x: (x,y) → (y,x)
  • To reflect over the line y=-x: (x,y) → (-y,-x)
  • To rotate 90° clockwise about the origin: (x,y) → (y, -x)
  • To rotate 180° clockwise about the origin: (x,y) → (-x,-y)
  • To rotate 90° counter-clockwise about the origin: (x,y) → (-y,x)
  • Reflection over Parallel Lines Theorem: Composing two reflections over parallel lines, h units apart, equals a translation of 2h units.
  • Reflection over the Axes Theorem: Two reflections over both axes result in a 180° rotation about the origin.
  • Reflection over Intersecting Lines Theorem: Two reflections over intersecting lines yield a rotation of 2x, centered at the point of intersection.

Glide Reflection

  • A glide reflection consists of a reflection followed by a translation, where the translation aligns with the direction of the reflection line.

Notation

  • Primes (e.g., A') denote the image of a point after a transformation.

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