geometry 1 area and circumference of a circle. central angle a central angle is an angle whose...

8
Geometry 1 Area and Circumference of a Circle

Upload: milo-marshall

Post on 03-Jan-2016

220 views

Category:

Documents


2 download

TRANSCRIPT

Geometry

1

Area and Circumference

of a Circle

Central AngleA central angle is an angle whose vertex is at the center of the circle.

2

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.

The arc measure is written as

Central Angle

A

B

CBAC

Circumference Example:

2 (3)CExample: Find the circumference of the following circle.

3 cm6C

18.85C cm

• When finding the circumference of a circle, you can leave your answer in terms of pi.

Circumference:

Circumference is the distance around the circle.

2C r

2 (3)C

4

C d2d r

Formula: Or

Example: Find the circumference of the following circle.

3 cm6C

18.85C cm

where

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.

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: 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.

Area of a Circle

Area of a circle is the number of unit squares that can fit into a circle.

2(3)A 9A

7

2A r

Example: Find the area of the following circle.

3 cm

228.27A cm

Formula:

Complete the table below and leave your answers in terms of pi.

Radius 8

Diameter

Circumference 26π

Area 18π