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Don't you just love related rates?

  1. Nov 20, 2005 #1
    The angle of elevation of the Sun is decreasing at a rate of 0.25 rad/h. How fast is the shadow cast by a 400-ft-tall building increasing when the angle of elevation of the Sun is π/6?

    I thought about using the special triangle to find exact values for trig functions at π/6 but I don't know which equation I should use to relate the rate of change. What should I do? :uhh:
  2. jcsd
  3. Nov 20, 2005 #2


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    Just write [itex]L = H \cot \theta[/itex] with the obvious definitions and differentiate.
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