The order of rotational symmetry is the number of times a figure can be rotated within 360° such that it looks exactly the same as the original figure. Draw a line segment MN joining the point M (-2, 3) and N (1, 4) on the. Now rotate PQ through 180° about the origin O in anticlockwise direction, the new position of points P and Q is: Thus, the new position of line segment PQ is PQ. Below are several geometric figures that have rotational symmetry. Solution: On plotting the points P (-3, 1) and Q (2, 3) on the graph paper to get the line segment PQ. Rotational symmetryĪ geometric figure or shape has rotational symmetry about a fixed point if it can be rotated back onto itself by an angle of rotation of 180° or less. 90 degrees counterclockwise rotation 180 degree rotation 270 degrees clockwise rotation 270 degrees counterclockwise rotation 360 degree rotation Note that a geometry rotation does not result in a change or size and is not the same as a reflection Clockwise vs. For 3D figures, a rotation turns each point on a figure around a line or axis. Two Triangles are rotated around point R in the figure below. The term "preimage" is used to describe a geometric figure before it has been transformed and the term "image" is used to describe it after it has been transformed.įor 2D figures, a rotation turns each point on a preimage around a fixed point, called the center of rotation, a given angle measure. On the right, a parallelogram rotates around the red dot. Let’s look at a real example, here we plotted point A at (5, 6) then we rotated the paper 90 clockwise to create point A’, which is at (6, 5). In the figure above, the wind rotates the blades of a windmill. If you take a coordinate grid and plot a point, then rotate the paper 90 or 180 clockwise or counterclockwise about the origin, you can find the location of the rotated point. Later, we will discuss the rotation of 90, 180 and 270 degrees, but all those rotations were positive angles and their direction was anti-clockwise.
A rotation is a type of rigid transformation, which means that the size and shape of the figure does not change the figures are congruent before and after the transformation. The -90 degree rotation is a rule that states that if a point or figure is rotated at 90 degrees in a clockwise direction, then we call it -90 degrees rotation. In geometry, a rotation is a type of transformation where a shape or geometric figure is turned around a fixed point. Home / geometry / transformation / rotation Rotation