1. 1.8: Perimeter, Circumference, and Area
Part I

2. Today’s Objectives
Solve for the perimeter or circumference of basic shapes
Use the distance formula to solve for the perimeter of basic shapes

3. Perimeter of Polygons
Perimeter – the sum of the lengths of a polygon’s sides a b c l w
𝑃=2𝑙+2𝑤
𝑃=𝑎+𝑏+𝑐

4. Finding the Perimeter of a Rectangle
What is the perimeter of a 13 by 6 rectangle?
l=13
w=6
𝑃=2(13)+2(6)
𝑃=26+12
𝑃=38

5. Circumference of a Circle
Circumference – distance around a circle r d
𝐶 =2𝜋𝑟 𝑜𝑟
𝐶=𝜋𝑑

6. Finding the Circumference of a Circle
What is the circumference of a circle with radius 5?
𝐶=2𝜋𝑟
r = 5
𝐶=2𝜋(5)
𝐶=10𝜋
𝐶=10(3.14)
=31.4

7. Perimeter on a Coordinate Plane
Find the perimeter of the triangle with vertices A(-3,4), B(1,-2), and C(5,5).
𝐴𝐵= 1−− −2−4 2
= −6 2 A C B =
= 52
=7.21
𝐵𝐶= 5− −−2 2 = =
= 66
=8.12
𝐴𝐶= 5−− −4 2 =
= 64+1
= 65
=8.06

8. Circumference on a Coordinate Plane
Find the circumference of the circle with a center C(-3,2) and contains the point A(0,3).
𝑟= 0−− −2 2
𝑟= − r A C
𝑟= 9+1
= 10
≈3.16
𝐶=2𝜋(3.16)
=19.84

9. Take Home Message Perimeter of polygons Circumference of circles
The distance formula can be used to solve other problems