Transformations are copies of a geometric shape that retain some properties of the original figure. They are similar to a figure that is copied and pasted on the computer. The pre-image refers to the original shape. The copy of the original shape is a transformation of the pre-image, and is called the image. If the image is exactly the same as the pre-image in size and shape, it is called a rigid transformation. Rotation is a type of transformation.
Spin a geometric shape around an axis, called the center of rotation, to perform a rotation transformation. Traditional convention dictates that rotations must move counterclockwise from the starting point. The distance of a specific point of the geometric figure, to the center of rotation, is always the same throughout the rotation. That point, followed throughout a complete rotation, makes a circle.
Rotations are measured in degrees. A complete circle has 360 degrees. Since the geometric figure moves on an axis around a central point, a complete rotation of the figure travels around a circle back to its starting point. A complete rotation is 360 degrees. Measure partial rotations by how many degrees the geometric figure moves from the starting point. Use a protractor to measure the degrees of rotation.
A geometric shape that looks identical after rotating is transformed by rotational symmetry. An airplane propeller has rotational symmetry. Each time a particular blade moves the distance between its center and the center of the blade next to it, the figure looks identical. Each time the figure moves to another point where it looks identical is called an order. If the propeller has two blades, the figure is order two. If it has four blades, it is order four.