1. SIMILAR FIGURES

2. ISOMETRIC VS SIMILAR -corresponding sides congruent
-corresponding angles congruent
-corresponding sides proportional
-corresponding angles congruent
These are IDENTICAL SHAPES moved by 4 isometries
translation (t)
rotation (r)
reflection (s)
glide reflection (gr)
DILATATION
- enlarge or reduce from initial
(1st) to image (2nd).
Think of a photocopy machine
K is the symbol for ratio of similarity

3. To Find K (ratio of similarity)5 10 15
initial 2 3
image 1
Ratio : measure of image
measure of initial
Ratio: 1 or 2 or 3
Ratio: is K= 0.2
To find the ratio of similarity, use corresponding side lengths.

5. Side lengths could be: radius diameter circumference height width
perimeter
apothem
ANY ONE DIMENSIONAL LENGTH

6. Ratio of Perimeter of Similar Figures
6 cm
4 cm
12 cm
8 cm
initial
image
Perimeter=20
Ratio of sides = 12 = 2 (this is the ratio of corresponding sides)
K = 2
Ratio of perimeters: K = 2
To find perimeter of image:
Perimeter of initial x K = perimeter of image
x = 40

7. Find the perimeter of the image of these
24 cm
Find the perimeter of the image of these
similar right triangles.
10 cm
6 cm
initial
Step 1- Find missing side on initial triangle.
(use Pythagoras or remember the triples)
Missing side = 8 cm
Step 2 – Find K = K = 3 8
Step 4- Calculate the perimeter of
the image
P initial X K = P initial
24 X 3 = 72
Step 3- Calculate the perimeter of
the initial
P =
P = 24

8. Finding the Area of Similar Solids
Area of initial X K2 = Area of image 6
image 5 2
initial
Step 1 – Find K = 3 2
Step 2 – Find area of image
(2 x 5) X 22 = 40 cm2