Rotation in a Plane

Rotation in a Plane

Movement of a figure about a fixed point, at a given angle, often expressed in degrees. The angle is called the angle of rotation.

Transformation of a plane defined by a fixed point O, called the “centre of rotation”, and a real number α, called the “angle of rotation”. This transformation maps a point P to a point P’ so that segments OP and OP’ are congruent and the measure of the angle formed by rays OP and OP’ is the absolute value of α.


Properties

  • A rotation is defined by a fixed point called the centre of rotation and a angle of rotation.
  • Rotations may be used to create frieze patterns and tessellations.
  • A rotation in a clockwise direction is a negative rotation.
  • A rotation in a counterclockwise direction is a positive rotation.

The invariants under a rotation of the plane are the following :

Rotations preserve:

A rotation does not preserve parallelism between a segment and its image.

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