Parts of a Circle

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Parts of a Circle - PowerPoint PPT Presentation

Parts of a Circle. 9.1 cm. 21 km. 4 cm. 13.8 cm. 9 km. Simplify . 4 2 (5)(3) 2 29 – 5 2 Calculate the area. Circle : The set of all points the same distance from a point called the center. Center : The middle of a circle.

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PowerPoint Slideshow about 'Parts of a Circle' - amal

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Presentation Transcript

9.1 cm

21 km

4 cm

13.8 cm

9 km

Simplify.

• 42
• (5)(3)2
• 29 – 52

Calculate the area.

Circle:

• The set of all points the same distance from a point called the center.
• Center: The middle of a circle.
• Radius: The distance from the center of a circle to any point on the edge.
• Chord: A line segment with endpoints on the circle.
• Diameter: The distance across a circle through the center.

Central Angle:

An angle with its vertex at the center of the circle.

Videos ~ SAV Lesson 3 ~ Parts of circle
Example 1

Use C to name each circle part.

A chord

• AB or EF

• CD or CE or CF

A diameter

• EF

Central Angle

• ∠ECD or ∠FCD or ∠FCE
Example 2

The diameter of a circle is 12 centimeters. Find the radius.

• Radius is half the diameter. 12 ÷ 2 = 6
• The radius is 6 cm.

The radius of a circle is 7 inches. Find the diameter.

• Diameter is double the radius. 7•2 = 14
• The diameter is 14 inches.
Example 3

Find the measure of the missing

central angle.

• The sum of the central angles is 360.
• Write an equation. 140 + 40 + 100 + x = 360
• Combine like terms. 280 + x = 360
• Subtract. –280 – 280x = 80
• The missing central angle , x, is 80⁰.

How many degrees are in a circle?

• Name the longest chord in A.
• Draw M with radius AM, diameter PR and chord XY.
Communication Prompt
• Why is the diameter the longest chord in a circle?
• Why is proper notation important?