1. The area of the isosceles triangle is 31 in2. Find the perimeter.
Mrs. Reulbach
Please write your name on the top line of the index card. Then, draw and label the triangle.
The area of the isosceles triangle is 31 in2. Find the perimeter.
8 in
6.2 in
Draw this diagram in your notebook.
What do you notice?
26 in

2. Mrs. Reulbach
Please write your name on the top line of the index card. Then, draw and label the triangle.
The area of the isosceles triangle is 31 in2. Find the perimeter.
8 in
8 in
6.2 in
10 in
26 in

3. Mrs. Reulbach
Draw this diagram in your notebook.
What do you notice?

4. What shape can you split a regular polygon into?
Mrs. Reulbach
Regular Polygon
Equilateral - all sides are equal
- Equiangular - all angles are equal
What shape can you split a regular polygon into?
Equilateral triangles
SAY, all sides and all angles are equal.
Regular polygon.

5. Mrs. Reulbach Vocabulary Equilateral triangle s Side (s) for the base
Apothem (a)
Length of a perpendicular segment from the center of the polygon to a side s a h s b s

6. Find the area of the regular polygon
Mrs. Reulbach
Find the area of the regular polygon
Find the area of the equilateral triangle.
35.1cm2
35.1cm2
35.1cm2
Find the area of the regular polygon.
7.8 cm
s = 9 cm
35.1cm2
35.1cm2
35.1cm2
Use SECOND one cm squared

7. Mrs. Reulbach s s s s a s s Find the area of the equilateral triangle.
Find the area of the regular polygon. s s a
What is the perimeter of this
regular polygon? s s
P =
s + s + s + s + s + s
P = 6s

8. Mrs. Reulbach
# of Sides P
Area 6 7 8 n s a

9. Mrs. Reulbach
# of Sides P
Area 6 7 8 n s a
Write the area formula.

10. Mrs. Reulbach
Write the area formula. s a

11. Find the area of the regular polygon.
Mrs. Reulbach
Find the area of the regular polygon.
7 in
7.3 in
in squared

12. Mrs. Reulbach The apothem of a regular octagon is 6 cm.
What is the length of each side of the octagon if the area is 120 cm2 ?
A= 120cm2
6 cm
40 = P
S = 5 cm
5 cm

13. What is the perimeter of this regular polygon?
Mrs. Reulbach
What is the perimeter of this
regular polygon? s
P =
s + s + s + s + s + s
P = 6s s s
Find the area of the regular polygon s s
7.8 cm
35.1 for triangle.
210.6 cm squared
s = 9 cm s

14. Mrs. Reulbach a s Find the area of the equilateral triangle.
Find the area of the regular hexagon. s a