Definition:Segment of Circle/Angle of Segment

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Definition

In the words of Euclid:

An angle of a segment is that contained by a straight line and a circumference of a circle.

(The Elements: Book $\text{III}$: Definition $7$)

That is, it is the angle the base makes with the circumference where they meet.


It can also be defined as the angle between the base and the tangent to the circle at the end of the base:

AngleOfSegment.png