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Chapter 10 - NCPN

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Arc Length<br />

The unit circle has a radius of 1 unit<br />

and is centered about the origin.<br />

A central angle of a circle is an<br />

angle with a vertex at the center of<br />

the circle. An intercepted arc is the<br />

part of the circle that has endpoints on<br />

the sides of the central angle and all<br />

points in the interior of the angle.<br />

Arc Length<br />

If a circle with radius r has a central angle of measure<br />

θ radians, the length, l, of the intercepted arc is l = rθ.<br />

Example 2<br />

Measuring Arc Length<br />

Find the length of the intercepted arc<br />

in the circle.<br />

Solution<br />

The measure of the central angle is 1.9 radians, and the circle has a radius of<br />

6 centimeters. Use the formula for the length of an intercepted arc.<br />

l = rθ<br />

l = (6)(1.9)<br />

l = 11.4<br />

The length of the intercepted arc is 11.4 centimeters.<br />

<strong>10</strong>.2 Evaluating Trigonometric Functions 443

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