Definition:Segment of Circle/Angle in Segment

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Definition

In the words of Euclid:

An angle in a segment is the angle which, when a point is taken on the circumference of the segment and straight lines are joined from it to the extremities of the straight line which is the base of the segment, is contained by the straight lines so joined.

(The Elements: Book $\text{III}$: Definition $8$)

And, when the straight lines containing the angle cut off a circumference, the angle is said to stand upon that circumference.

(The Elements: Book $\text{III}$: Definition $9$)


AngleInSegment.png

Such a segment is said to admit the angle specified.