Answer: 3 radians (choice C)
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Work Shown:
- L = arc length = 12 cm
- theta = angle in radians = unknown
- r = radius = 4 cm
L = theta*r
12 = theta*4
12/4 = theta
3 = theta
theta = 3 radians, choice C is the answer.
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Side note: The formula L = theta*r only works if theta is in radians.
If theta is in degrees, then use L = (theta/360)*2pi*r. So you can see that radian mode is much easier in this case.
