Transcript Sec. 8 – 2 Similar Polygons

Sec. 6–2
Similar Polygons
Figures that are similar (~) have
the same shape but not
necessarily the same size.
Angles are congruent,
Sides are proportional
If two figures are similar, not only are their
sides proportional, all their linear parts are
proportional (such as the height, median,
midsegment, diagonals, etc).
Writing a similarity statement is like writing a congruence
statement—be sure to list corresponding vertices in the
same order.
Scale Factor:
If two polygons are similar, then the
ratio of the lengths of two corresponding
sides is called the scale factor.
1. The two triangles are similar, find
the missing angles
50°
120°
2. Triangle ABC ~ Triangle DEF,
find x and y.
D
3
A
x
18
10
C
2
E
B
y
F
3. Two similar rectangles have sides in the
ratio of 3 : 7. If the smaller rectangle has
a perimeter of 50m, find the perimeter of
the larger rectangle.
4. Are these polygons similar (the sum of the
angles in a pentagon is 540◦)?
2.4
130◦
5.5
1.9
110◦
130◦
100◦
110◦
6
3.1 100◦ 100◦
3.1
2.9
4.6
100◦
2.9
5
Determine whether the polygons are
similar. If so, write the similarity ratio
and a similarity statement and find the
scale factor from quad ABCD to quad EFGH.