enlargement_1111111111111111111111111.ppt

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1. EnlargementEnlargement
Objectives:
C Grade Find the centre of enlargement
F Grade Give a scale factor of an enlarged shape
E Grade Enlarge a shape by a positive scale factor
Find the measurements of the dimensions
of an enlarged shape
D Grade Enlarge a shape by a positive scale factor
from a given centre

2. EnlargementEnlargement
A 2-D shape can be made larger by a given amount
This is called the Scale Factor
w
l
2w
2l
Notice how the sides
of the image are twice
that of the object
This is an enlargement
scale factor 2
object
image
If the length the sides was increased to be 3 times as long
the scale factor would be 3

3. EnlargementEnlargement
Objects can be enlarged using the scale factor to extend the length
of the sides, because it is the sides that are increased it is called the
linear scale factor.
This name is only important when the area and / or volume are
part of the consideration for enlargement.
As was seen by finding the length of the image side by:
image line length = object line length × scale factor
similarly
linear scale factor = object line length
image line length

4. EnlargementEnlargement
Now do these:
Enlarge these shapes alongside by a scale factor of 2
1. 2. 3.
Enlarge these shapes below by a scale factor of 3
4. 5.

5. EnlargementEnlargement
Identify the scale factor used to enlarge these shapes
6. 7. 8.
scale factor 3
scale factor 4
scale factor 2.5

6. EnlargementEnlargement
Normally an enlargement is required given a centre of enlargement.
Using the centre of enlargement locates the image.
object
Draw construction lines from the centre of enlargement CoE
through the vertices of the object.Ray Lines
CoE
Using a scale factor 2 the distance from the CoE to the image
vertices is 2 times the distance from the CoE to the object vertices.
2 squares right
1 square down
Scale Factor 2
Distance from CoE
4 squares right
2 squares down
x
5 squares right
1 square down
Scale Factor 2
Distance from CoE
10 squares right
2 squares down
x
2 squares right
3 squares down
Scale Factor 2
Distance from CoE
4 squares right
6 squares down
x
This gives us enough information to draw the image

7. EnlargementEnlargement
Repeat this to see the effect of a scale factor 3
objectCoE
2 squares right
1 square down
Scale Factor 3
Distance from CoE
6 squares right
3 squares down
x
5 squares right
1 square down
Scale Factor 3
Distance from CoE
15 squares right
3 squares down
x
2 squares right
3 squares down
Scale Factor 3
Distance from CoE
6 squares right
9 squares down
x
This gives us enough information to draw the image

8. EnlargementEnlargement
The position of the centre of enlargement relative to the object makes a
difference as to where the enlarged image is positioned.
CoE
CoE
CoE
CoECoE
CoE
CoE
CoE
Moving the centre of enlargement up moves the image downMoving the centre of enlargement away from the object moves the image further
away in the opposite direction
Moving the centre of enlargement down moves the image up
CoE

9. EnlargementEnlargement
Find the coordinates of the centre of enlargement by drawing the ray lines
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