Page 165 - Mathematics Coursebook

17.2 Rotating shapes

17.2 Rotating shapes

When you rotate a shape you turn it about a "xed point
called the centre of rotation.

You can rotate a shape clockwise or anticlockwise.
You must give the fraction of a whole turn, or the number
of degrees, by which you are rotating the object. clockwise anticlockwise

!e turns that are most o#en used are a quarter-turn (90°),
a half-turn (180°) or a three-quarters turn (270°).

Worked example 17.2
a Draw the image of this shape after a b Describe the rotation that takes shape
rotation of 90° clockwise about the A to shape B.
centre of rotation marked C. y
6
5
4 A
3
C 2
1 B
0
01 23 45 6 x

a

C C
C C

C
Start by tracing the shape, then C Start turning the tracing paper 90°
C
C
put the point of your pencil on (a quarter-turn) clockwise.
the centre of rotation. object
object
C C
C C C
C C C object
object
image image
C C
C C C
C C C
image image
Once the turn is completed make Draw the image onto the grid.
a note of where the image is.

b Rotation is 180° (or a half-turn). When you describe the rotation, give the number of
degrees and the coordinates of the centre of rotation.
The centre of rotation is at (3, 3). Note that when the rotation is 180° you don’t need to
say clockwise or anticlockwise as both give the same
result.

164 17 Position and movement