1. Area and Circumference of a Circle
Geometry
Area and Circumference
of a Circle

2. Central Angle
A central angle is an angle whose vertex is at the center of the circle.
The arc measure is written as
The measure of a minor arc is the measure of its central angle.
The measure of a major arc is 360 minus the measure of its central angle.

3. Circumference: Circumference is the distance around the circle.
Formula: Or
where
Example:
Find the circumference of the following circle.
3 cm

4. Circumference Example:
Find the circumference of the following circle.
3 cm cm
When finding the circumference of a circle, you can leave your answer in terms of pi.

5. Example: The rim of a satellite dish has a diameter of 7 feet
Example: The rim of a satellite dish has a diameter of 7 feet. Find the circumference of the rim and the area of the circle defined by the rim. Use 3.14.
Example: If a bicycle tire has a diameter of 26 inches, how far does it travel in 1000 revolutions of the tire? Use 3.14.

6. Example: A Ferris wheel has diameter of 42 feet
Example: A Ferris wheel has diameter of 42 feet. How far will a rider travel during a 4 minute ride if the wheel rotates once every 20 seconds? Use 22/7.
Example: The tires of a racing bike are approximately 70 cm in diameter. How far does a bike racer travel in 5 minutes if the wheels are turning at a speed of 3 revolutions per second? How many revolutions does a wheel make in 22 km race? Use 22/7.

7. Area of a Circle
Area of a circle is the number of unit squares that can fit into a circle.
Formula:
Example:
Find the area of the following circle.
3 cm

8. Complete the table below and leave your answers in terms of pi.
Radius 8
Diameter
Circumference
26π
Area
18π