Page 204 - ICSE Math 7

Y
5 A(4, 5)
4

Example 3: Find the reflection of triangle ABC in x-axis. B(–1, 3) 3
2
1 C(7, 2)
X' O X
–5 –4 –3 –2 –1 1 2 3 4 5 6 7
–1
Y'

Y
5 A(4, 5)
4
B(–1, 3) 3
Solution: Reflection of DABC in x-axis is DA'B'C' with 2
A'(4, –5), B'(–1, –3) and C'(7, –2). 1 C(7, 2)
X' O X
–5 –4 –3 –2 –1 1 2 3 4 5 6 7
–1 C'(7, –2)
–2
B'(–1, –3) –3
–4
–5 A'(4, –5)
Y'
Example 4: Plot the reflections of line segment PQ in
the y -axis where P = (–3, –6) and Q = (–2, 4). Y
Q(–2, 4) 4 Q'(2, 4)
Solution: Reflection of PQ in y-axis is given by P'Q' where 3
P' = (3, –6) and Q' = (2, 4). 2
1
X' O X
–5 –4 –3 –2 –1 1 2 3 4 5
–1
–2
–3
–4
–5
P(–3, –6) –6 P'(3, –6)
Y'
Rotation

Rotation is a transformation which rotates all the points in a plane
about a fixed point through a given angle. In our day-to-day life we Maths Info
come across objects which rotate around a point, such as a bicycle The shape and size of a figure
wheel, blades of a ceiling fan, blades of a windmill, etc. The fixed doesn’t change after rotation.
point about which the object rotates is called the centre of rotation.
There are two types of rotation. Anticlockwise
rotation
(i) Clockwise: If rotation of an object is in the direction of motion
of the hands of a clock, it is called clockwise rotation.
O
(ii) Anticlockwise: If an object rotates in the direction of motion
opposite to that of the hands of a clock, it is called anticlockwise Clockwise
rotation. rotation

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