Page 194 - Maths Class 05

Rotation

Rotation means turning. In geometry, rotating a figure means turning a figure about a

given point that is known as the centre of rotation . This point can be on the figure or
any other point.

Some examples of rotation from real life situations are :

12 12

9 3 9 3

6 6

Rotation of the hands of a clock Steering wheel of Knob of a door Windmill
about the point where they meet a car about the centre

You can also rotate 2-D shapes or plane shapes about a point. Three things are needed to

describe a rotation :

H The direction of rotation – clockwise or anti-clockwise

H The angle of rotation H The centre of rotation

The example given below shows the rotation of a square about a given point. The square

has been further divided into coloured squares to make you understand clearly its
movement.

One Quarter Turn Half Turn Full Turn

Square D comes
A A A
to position A

D
90°
90° 90° 90°
Centre of 180°
P P P
rotation 90° 90° 90°
B B B
Square A comes to position B

Square B comes to position C C Square C comes to position D C

Shape A is rotated through Shape B is further rotated through an angle of 90° about the
Shape C is again rotated
an angle of 90° about the same point P in the clockwise direction to get shape C.
by an angle of 90° about
point P in the clockwise This is the same as if we would rotate shape A through an angle
point P to get shape D.
direction to get shape B. of 180° about point P in clockwise direction to get shape C.

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