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2. Central Angle and Perimeter

- Definition Central Angel and Perimeter
- The central angle of a circle is an angle where the vertex is at the center of the
circle, while the circumferential angle is an angle where the vertex lies on the
circumference of the circle. The image of the center angle and the circumference
angle can be seen in the following figure.

Based on the picture above, it is known that:
AOB = Center Angel
OBC = Perimeter

- Relation Center angle and Perimeter
a. The central angle is equal to twice the circumferential angle if they
both face the same arc and the circumferential angle is half of the
central angle that faces the same arc, as shown in the figure below.

AOB is the angle at the center of the circle and ACB is the angle at
the circumference. The central angle AOB and the circumferential
angle ACB face the same arc, i.e. AB

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