Zusammenfassung der Ressource
transformations
- Enlargement
[clip 76]
- Enlargement
with a point of
enlargement
- This means that the
enlargement has to be
the right size and in
the right position
- Example: scale factor 2
- Draw a guideline from the
centre of enlargement
through one of the points of
the shape
- Count how to get from the
centre to the point then
multiply this by the scale factor
- E.g centre to
Point A is
Across 1 Up 5
- For the enlargement this needs
to be done twice, so the new
position of A is Across 2 Up 10
from the centre of enlargment
- From the new position the
rest of the sides can be
worked out as before, by
multiplying them by the
scale factor
- Multiply each
side by the
scale factor
- E.g Scale
factor-2
................
side x 2
- B is the enlargement of
A by the scale factor 2
- This is
increases the
size of the
shape
- E.g Scale
factor 1/2
................
side x 1/2
(0.5)
- C is the enlargement
of A by scale factor 1/2
- Multiplying by 1/2
is the same has
dividing by 2. So the
size of the shape is
decreased
- When there is no
point of
enlargement, the
enlarged shape can
go anywhere
- Enlargement
by a negative
scale factor
[clip 171]
- Mark out the
centre of
enlargement
- Draw guidelines from the
orginial shape through the
centre and carry them on
- Count how to get from the centre
to the point then multiply this by
the scale factor
- Example: the
scale factor is -2
and the centre of
enlargement is
(1,0)
- Because the scale factor is a
negative the new shape is on
the opposite side of the centre
of enlargement than the
original shape
- Describing an
enlargement
- 1. name the
translation
2. work out
scale factor
3. find
centre of
enlargement
- if the shapes are
different sizes then it
is an enlargement.
- Divide the length of a side
from the enlarged shape by
the length of a side on the
original shape to work out
scale factor
- To find the centre of enlargement join two
like points with a line and carry it on. Do
this for 2 or more points.
- Where the
lines cross is the
centre of
enlargemrnt