1. CIRCUMFERENCE: or If you unwrap a circle, how long will the line be?
The distance around the circle.
If you unwrap a circle, how long will the line be? or
So what is  anyway?

2. AREA FORMULA r The area of a circle with radius r is given by
This gives us the EXACT number of squares! r
(It’s usually not a whole number.)

3. Fraction of a Circle
What fraction of the whole circle is a given arc?
Find the measure of the central angle.
Divide by 360, the total number of degrees in the circle.
180º
diameter
This arc is one-half of a circle.

4. Fraction of a Circle 140º 220º = 220º
What fraction of the whole circle is this (major) arc?
Find the measure of the central angle.
The major arc measure is:
360º – minor arc measure
= 360º - 140º
= 220º
Divide by 360, the total number of degrees in the circle.
140º
220º
This arc is eleven-eighteenths of a circle.

5. Arc Length Formula Arc Length
= (fraction of the circle) X (circumference)
= fr x C
= x 2r
= x 2r

6. Example: Find the Arc Length
A.L. (arc length)
= fraction *circ. =
Exact Answer (in terms of ) in in
Approximate Answer (nearest tenth)

7. SECTOR
sector of a circle - part of the interior of a circle bounded by two radii and an arc.

8. AREA OF A SECTOR
The area of a sector of a circle
The size of a slice of pizza.
The FRACTION OF THE CIRCLE multiplied by the AREA OF THE CIRCLE.

9. Area of a Sector Formula
= (fraction of the circle) X (area of circle)
= fr x A
= X r2

10. Example: Find the Area of the Sector
A.S. (area of a sector)
= fraction *area
72°
Exact Answer (in terms of )
in2
Approximate Answer (nearest tenth)
in2