Linear Algebra THURSDAY, AUGUST 14

Learning Target I will understand what is meant by turn or rotational symmetry and how each point in a figure is related to its image under transformation by rotation.

Rotational Symmetry  Rotational symmetry : A figure or design has rotational symmetry if it can be rotated less than a full turn about a point to a position in which it looks the same as the original. The design below has rotational symmetry with its center as the center of rotation and a 60 o angle of rotation. This means that it can be rotated 60 o, or any multiple of 60 o, about its center point to produce an image that matches exactly with the original.

Rotational Symmetry  Rotation: A transformation that turns a figure counterclockwise about a point. Polygon A’B’C’D’ below is the image of polygon ABCD under a 60 o rotation about point P. If you drew a segment from a point on polygon ABCD to point P and another segment from the point’s image to point P, the segments would be the same length and they would form a 60 o angle The line segment D’ to P and D to P are of equal length. The angle formed is 60 o

Rotational Symmetry  Center of rotation : A fixed point about which a figure rotates. Center of rotation

Rotational Symmetry  Angle of rotation: The number of degrees that a figure rotates. In the example below the angle of rotation is 90 o. ABC is rotated counterclockwise 90 o about point P to result in image A’B’C’.