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In circle O, radius OQ measures 9 inches and arc PQ measures 6π inches. Circle O is shown. Line segments P O and Q O are radii with length of 9 inches. Angle P O Q is theta. What is the measure, in radians, of central angle POQ?

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Answer:

2π/3 rad

Explanation:

To get theta, we will apply the formula for calculating the length of an arc as shown;

Length of an arc = theta/360 * 2πr

theta is the central angle (required)

r is the radius of the circle

Given r = 9 inches and length of the arc PQ = 6π in

Substituting this given values into the formula to get the central angle theta;

6π = theta/360 * 2πr

Dividing both sides by 2πr

theta/360 = 6π/2πr

theta/360 = 3/r

theta/360 = 3/9

theta/360 = 1/3

cross multiplying;

3*theta = 360

theta = 360/3

theta = 120°

Since 180° = π rad

120° = x

x = 120π/180

x = 2π/3 rad

Hence the measure of the central angle in radians is 2π/3 rad

User Asumu Takikawa
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