The Lesson
All triangles drawn from a chord in a circle make the same angle at the circumference.
How to Use the Circle Theorem where the Angles in the Same Segment Are Equal
Question
What is the angle θ in the circle below?
Step-by-Step:
1
The angles subtended by the chord at the circumference of the circle are equal.
θ = 40°
Answer:
The angle θ is 40°.Useful Definitions
A semicircle is half a circle. A chord is a line whose endpoints lie on the circle.
A segment is a region, not containing the center, bounded by a chord and an arc lying between the chord's endpoints.
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