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Homework Help: Adv. Functions question please help

  1. Sep 1, 2010 #1
    The tide in a local costal community can be modelled using a sine function. Starting at noon, the tide is at its "average" height of 3 metres measured on a pole located off of the shore. 5 hours later is high tide with the tide at a height of 5 metres measured at the same pole. 15 hours after noon is low tide with the tide at a height of 1 metre measured at the same pole. Use this information to model the tide motion using a sine function. Show all work.
     
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  3. Sep 1, 2010 #2

    Office_Shredder

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    What have you tried so far? Do you know what a general sinusoidal function is going to look like in equation form?
     
  4. Sep 1, 2010 #3
    i know the period is 12 hours which will be pi/6 in the equation
    im pretty sure the amplitude is 2
    so i know its going to be something like y=2sin(pi/6x)
    but thn i dont know the vertical shift or horizontal shift
     
  5. Sep 1, 2010 #4
    the phase shift is what im really having trouble with
     
  6. Sep 1, 2010 #5

    Office_Shredder

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    It says the average height of the tide is 3 meters. [tex]2 \sin(\frac{\pi}{6}x)[/tex] has an average height of 0 (it oscillates between -2 and 2). How much do you have to shift it up to get an average height of 3?

    For the phase shift, what time is x=0 going to correspond to?
     
  7. Sep 1, 2010 #6
    would you shift it up 3?
     
  8. Sep 1, 2010 #7
    is the answer y=2sin(pi/6x) +3?
     
  9. Sep 1, 2010 #8
    yesss.. nooo?? haha
     
  10. Sep 1, 2010 #9

    Office_Shredder

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    That could be right. The problem doesn't specify what time x=0 is at. So you get to pick. What time does x=0 represent?
     
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