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[apcalculus] Units of RADIANS per SecondRelated Rates Problem
Posted:
Oct 19, 2012 6:00 PM


NOTE: This apcalculus EDG will be closing in the next few weeks. Please sign up for the new AP Calculus Teacher Community Forum at https://apcommunity.collegeboard.org/gettingstarted and post messages there.  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 setup 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 WiedBrusky Mathematics Department Brookfield East High School Brookfield, Wisconsin 53005
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