8.50 Chapter 8
The figure shows an acute-angled triangle PQR with vertices
P(-1 , 2), Q(-3 , 1) and R(-1 , 0). P, Q and R are rotated about
the origin O through 180c to Pl, Ql and Rl respectively.
(a) Find the coordinates of Pl, Ql and Rl.
(b) Draw 3PlQlRl in the figure. Is PR parallel to PlRl?
Explain your answer.
19
Instant Drill
➥ Ex 8D 27
O
-3
x
y
P
Q
R
-2 -1 1
1
-1
-2
2
2 3
PracticePractice
Class 8.4
1. In the figure, mark the images Al, Bl, Cland Dlafter the following
translations and write down their coordinates.
(a) Point A is translated 5 units downwards to a point Al.
(b) Point B is translated 3 units upwards to a point Bl.
(c) Point C is translated 1 unit to the left to a point Cl.
(d) Point D is translated 4 units to the right to a point Dl.
2. In the figure, l is a horizontal line and L is a vertical line. Complete
the table below.
Original
point
Axis of
reflection
Coordinates of
the image
(a) A x-axis ( , )
(b) B y-axis ( , )
(c) A L ( , )
(d) B l ( , )
0 1
1
2
2
3
4
x
y
-1
-1
-2
-3
3
-2
-3
C
D
A
B
x
y
0 1
1
2
3
4
4 5 6
-1-1-2 -3
-3
-4
-4
-5
-6
32
-2 m
A
B
L
Please refer to the STEM Workshop
'Symmetrical Figure Creator Program'
in Appendix II on P.A10.
Section Test 8D
Pl(1 , -2), Ql(3 , -1), Rl(1 , 0)
(-3 , -3)
(1 , 2)
(2 , 1)
(2 , -1)
yes
Extra Example D
[on P.T8.76l ]
4
6
-4
-2
1
1
-5
-1
Q'
P'
R'
C'
D'
A'
B'