Section 9.3 Rotations
By Sean Lockwood, Louie Folgore, and Dan Striapko
Vocabulary
Center of Rotation-A fixed point around which shapes move in a
circular motion to a new position
Angle of Rotation-The angle through which a preimage is rotated to
form the image.
Free Form Rotations
How to Free form
Rotate
Rotations can be either
counterclockwise or clockwise, and go
about an origin. You should begin by
drawing your starting shape and your
origin. Then you draw a line segment
from a vertex to the origin. Then you
draw another line segment to make
the desired angle of rotation on the
end of the new line segment will be
the rotated point. Repeat this steps for
the rest of the vertices, and you will
have successfully rotated the shape.
Extra: if a problem does not state the
direction of the rotation then assume it is
counter clockwise.
Coordinate Plane rotations
90 Degree Rotation on Coordinate Plane
To rotate a point 90 degrees
counterclockwise about the origin,
you have to multiply the ycoordinate by -1 and then
interchange the X and Y
coordinates.
Formula:
180 Degree Rotation on Coordinate Plane
To rotate a point 180 degrees
counterclockwise about the
origin, multiply the X and Y
coordinates by -1.
Formula:
270 Degree Rotation on Coordinate Plane
To rotate a point 270 degrees
counterclockwise about the origin,
multiply the X-Coordinate by -1 and
then interchange the X and Y
coordinates.
Formula: