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Topic: [ap-calculus] Units of RADIANS per Second--Related Rates Problem
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Leanne Wied-Brusky

Posts: 6
Registered: 12/17/09
[ap-calculus] Units of RADIANS per Second--Related Rates Problem
Posted: Oct 19, 2012 6:00 PM
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I have a question about the units in a related rates problem. I insist on using units throughout a related rates problem to reinforce the proper set-up and understanding of an application problem.

When dealing with a rate of change of angle problem, how do units of radians/second suddenly appear? For instance, when we have the classic falling ladder problem:

cosA = (x ft)/(13 ft) and dx/dt = 2 ft/sec at the moment when x = 5 ft

How does dA/dt acquire units of RADIANS/sec?

Leanne Wied-Brusky
Mathematics Department
Brookfield East High School
Brookfield, Wisconsin 53005

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