# Arcs of a circle

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##### Intros
###### Lessons
1. Terms related to circles
• Diameter
• Circumference
• Central angle
• minor arc
• major arc
• Inscribed angle
• Chord
• perpendicular bisector
• Tangent
• point of tangency
2. How to find the length of an arc?
• by Central angle
• by Proportion
• by Using formula a = Θr

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##### Examples
###### Lessons
1. Find the length of the arc in red.

2. In the following circle, AD is diameter and BC $\bot$ EF, and the radius is 7. Find the measures of:
1. $arc AB$
2. $arc ABE$
3. $arc AEC$
4. $\angle BFD$
3. On circle D, arcAB= 105°, arcBC= 140° and arcABC= 245°. Point E is on the circle D too and arcCE= 145°. Explain what E must be on ArcAB.