Rectangular Coordinate System (I) 8.37
From Class Activity 8.3, we can see that:
For any point P(x , y),
(a) the coordinates of the image after P is translated n units to the
right are (x + n , y),
(b) the coordinates of the image after P is translated n units to the
left are (x - n , y).
(x - n,y) P(x,y) (x + n,y)
n units n units
Note: For translation to the left or right, the point P and its image lie
on the same horizontal line. Therefore, their y-coordinates are
the same.
II. Translation Upwards or Downwards
Take out the transparency film provided in the Activity Kit.
1. Place the film over the figure so that point P and the two axes coincide.
(a) Move the film upwards by 2 units. Denote the image of P by Pl.
Coordinates of Pl = ( , )
(b) y-coordinate of Pl = y-coordinate of P +
x-coordinate of Pl ( = / ! ) x-coordinate of P
2. Place the film over the figure so that their axes coincide respectively.
(a) Move the film downwards by 3 units. Denote the image of P by Pm.
Coordinates of Pm = ( , )
(b) y-coordinate of Pm = y-coordinate of P -
x-coordinate of Pm ( = / ! ) x-coordinate of P
ActivityActivity
Class 8.4 Class e-Activity
P(1,3)
-1 1
1
0 2 3
-1
2
3
4
5 y
x
PPl is a vertical line.
◀
P(1,3)
-1 1
1
0 2 3
-1
2
3
4
5 y
x
PPm is a vertical line.
◀
Teachers may also use GeoGebra
to conduct the activity.
1
1
2
3
5
0