8.48 Chapter 8
(b) Diagram Clue
R(- 2,5)
O
S 90° y
x
Coordinates of S
= (,)52--
(a) A(-3 , 4) is rotated anticlockwise about the origin O through
270c to a point B. Find the coordinates of B.
(b) C(6 , -3) is rotated about the origin O through 180c to a point D.
Find the coordinates of D.
17
Instant Drill
➥ Ex 8D 8-12
Public Exam
Questions 1-6
In the figure, B(4 , -5) is obtained when a point A is
rotated anticlockwise about the origin O through 90c.
(a) Find the coordinates of A.
(b) A is reflected in the y-axis to a point C. Wilson
claims that C coincides with B. Do you agree?
Explain your answer.
(a) Let (x , y) be the coordinates of A,
then -y = 4
y = -4
x = -5
` The coordinates of A are (-5 , -4).
Alternative
A is the image when B(4 , -5) is rotated clockwise
about the origin O through 90c.
` Coordinates of A = (,)54
--
Level 2
Example 18
Explain
y
x
O
B(4 ,- 5)
Solution Diagram Clue
y
x
O
B(4,-5)
A
Diagram Clue
y
x
O
B(4 ,- 5)
A
from A to B
from B to A
[ Objective: Question related to rotation in a rectangular coordinate
plane.]
(4 , 3)
(-6 , 3)
Supp Example 18
[on P.T8.76h]