# By Lisa Budi Rahayu, SSi. Rotation Rotation occurs when an object is turned around a given point Rotation can be clockwise or anti-clockwise The fixed.

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By Lisa Budi Rahayu, SSi

Rotation Rotation occurs when an object is turned around a given point Rotation can be clockwise or anti-clockwise The fixed point is called the centre of rotation the angle through which the shape is rotated is called the angle of rotation

Properties of rotation Anti-clockwise rotation is positive and clockwise rotation is negative A rotation through 180 0 is a half turn, a rotation through 90 0 is a quarter turn A point and its image are equidistant from the centre of rotation Each point of an object moves along the arc of a circle whose centre is the centre of rotation Only the centre of rotation is invariant The object and the image are directly congruent

The perpendicular bisector of a line joining a point and its image passes through the centre of rotation A line segment and its image are equal in length

Exercise on Cambridge Book Page : 252 Assessment

Enlargement Enlargement is a transformation in which each point of an object is mapped along a straight line drawn from a fixed point The fixed point is called the centre of enlargement The distance each point moves is a certain number multiplied by its distance from the center of enlargement SF = image length_ original length

Properties of enlargement The centre of enlargement can be anywhere A scale factor greater than 1 enlarges the object whilst a scale factor smaller than 1 reduce the object

If a point and its image are on opposite sides of the centre of enlargement, then the scale factor is negative An object and its image are similar with sides in the ratio 1 : k; where k is the scale factor The areas of the object and its image are in the ratio 1 : K 2 Angles and orientation of the object are invariant

Exercise on Cambridge Book Page : 254 Assessment

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