Circle Formulas

1
Chapter 10

• Circle Formulas

• Circumference
• Arc Length
• Area
• Sector

2
Circumference

• Circumference is the distance around the circle.

Formula
Or
where
Example
Find the circumference of the following circle.
cm
3
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.
4
Central Angle Example
5
Arc Length

• Arc length is the distance around an arc.

The circumference multiplied by the ratio of the
center angle and 360.
Formula
Example
Arc Length
6
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.
7
Area of a Sector

• Area of a sector is the area of a section of the
  circle.

The area multiplied by the ratio of the center
angle and 360
Formula
Example
Sector
65
8
Congruent Arcs and Chords

• In a circle or ? circles, 2 minor arcs are ? iff
  corres chords are ?.

9
SAT Example
10
?Chords and Radii
11
? Chords and Radii Example