Download Discovering Geometry Day 49

Discovering Geometry
Day 49
7.1 Transformation and Symmetry
o Daily Openers
o Check homework
7.1 Transformation and Symmetry
transformation – movement of a figure.
preimage – the original figure.
image – new figure after the transformation.
rigid transformation – image is  to the preimage.
nonrigid transformation – transformation does not preserve the size and shape.
isometry – rigid transformation. A transformation where the preimage remains the same
size and shape.
Types of Transformations
1. translation – slide, composed of a vertical and horizontal movement
called a vector.
2. reflection – flip, mirror image, drawn by moving points  across a line of reflection.
REFLECTION LINE CONJECTURE
The line of reflection is the ______ of every segment joining a point in the original
figure with its image.
3. rotation – turn, each point turns an identical number of degrees around a fixed
center point. Rotation can be either clockwise or counterclockwise.
ROTATIONAL SYMMETRY
When a figure can be rotated about a point in such a way that its rotated image
coincides with the original figure before turning a full 360˚.
Ex. Plot the points A(1, 2), B(2, 5), and C(3, -2)
Translate the points by the vector:
 4, 2
Ex. Reflect the point across the y-axis.
Ex. Reflect the point across the line y = 2
Ex. Rotate the figure 90˚ clockwise.
Ex. Rotate the figure 180˚ counterclockwise.
Glide Reflection – combination of a translation and a reflection.

Practice Reflections and Rotations on Patty Paper.
Homework – page 372 – 373 #1 – 14, 16
Daily Openers – 1.–3. page 362 #41, 42, 43
4. –5. pages 374–375 #17, 21