## central angle

### A central angle is an angle with its vertex at the center of a circle and its rays extending to the circumference of the circle

A central angle is an angle with its vertex at the center of a circle and its rays extending to the circumference of the circle. It is also known as a radial angle or a angular section.

To understand central angles better, it is important to know a few key terms associated with a circle:

1. Center: The point within a circle that is equidistant from all points on the circumference.

2. Circumference: The boundary of a circle, which is the distance around it.

3. Radius: The distance from the center of the circle to any point on the circumference. It is denoted by “r”.

4. Diameter: The distance across the circle passing through the center. It is twice the radius, denoted by “d” (d = 2r).

Now, let’s consider a circle with its center point “O.” Suppose we draw a central angle with vertex “O” and rays extending to two points on the circumference of the circle, creating an angle within the circle.

The measure of a central angle is defined by the amount of rotation between the two rays of the angle, measured in degrees (°). A complete rotation around a circle is 360°. So, a full central angle intercepts an arc whose length is equal to the circumference of the circle.

The relationship between the measure of the central angle and the arc it intercepts is proportional to the ratio of the measure of the central angle to 360°. Mathematically, we can represent this relationship as follows:

(arc length intercepted by the central angle) / (circumference of the circle) = (measure of central angle) / 360°

This formula can be rearranged to find the arc length intercepted by a central angle:

arc length = (measure of central angle / 360°) * (circumference of the circle)

It’s important to note that if the central angle measures exactly 360°, then the arc length intercepted is the entire circumference of the circle. On the other hand, if the central angle measures less than 360°, the arc length intercepted will be proportional to the angle measure.

Overall, central angles play a fundamental role in understanding circles and their properties. They are used to measure and relate angles, arc lengths, and circumferences within a circle.

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