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anonymous

  • one year ago

Related Rates The sailor sails his boat at a constant speed of 12km/h staying 4km from and parallel to a straignt shoreline. How fast is the boat approaching a lighthouse on shore where boat 5km from the lighthouse?

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  1. Loser66
    • one year ago
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    pic?

  2. anonymous
    • one year ago
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    |dw:1433040585514:dw| I'm not sure though...

  3. Loser66
    • one year ago
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    |dw:1433040673042:dw|

  4. anonymous
    • one year ago
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    oh, okay

  5. Loser66
    • one year ago
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    I think just take distance/ velocity = time

  6. anonymous
    • one year ago
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    The 12km/h, is going negative?

  7. Loser66
    • one year ago
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    how?

  8. Loser66
    • one year ago
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    12km/h = 12km/ 60 minutes, that is 1minute/ 0.2 km you have 5 km, then, it takes 25 minutes to finish the distance, right?

  9. anonymous
    • one year ago
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    I remember something about -12km/h from my teacher, but I'm not sure though.

  10. Loser66
    • one year ago
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    if velocity has negative sign, that shows the replacement is opposite way to what you define positive direction. In this case, they use "speed" not velocity, hence, no negative here, period.

  11. rational
    • one year ago
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    hey still stuck on this

  12. anonymous
    • one year ago
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    Yes @rational I'll be right back, I have to eat dinner

  13. anonymous
    • one year ago
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    I'm back @rational

  14. amistre64
    • one year ago
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    so want to know the rate of change of the 'hypotenuse' of this triangle; what can we use to model the length of the hypotenuse?

  15. amistre64
    • one year ago
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    |dw:1433045913122:dw|

  16. amistre64
    • one year ago
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    d^2 = b^2 + 4^2 implicit derivative gives us 2d d' = 2b b' d' = b' b/d we know b' and b, and can determine d

  17. amistre64
    • one year ago
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    or we know b' and d ... and can determine b either way

  18. anonymous
    • one year ago
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    b=3?

  19. anonymous
    • one year ago
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    |dw:1433046508888:dw| ???

  20. anonymous
    • one year ago
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    @amistre64

  21. anonymous
    • one year ago
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    @rational

  22. anonymous
    • one year ago
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    Given dx/dt =12km/h, find dz/dt=? when z=5km x^2+y^2=z^2 (2x)(dx/dt)+(2y)(dy/dt)=(2z)(dz/dt) ???

  23. anonymous
    • one year ago
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    May the answer be 36/5=dz/dt??

  24. rational
    • one year ago
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    36/5 looks good!

  25. anonymous
    • one year ago
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    My teacher said something about -12km/h, but dont know why...

  26. anonymous
    • one year ago
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    Should it be -36/5km/h?? hmmm... :/

  27. anonymous
    • one year ago
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    @rational ??

  28. rational
    • one year ago
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    yes, because the distance between lighthouse and boat is reducing

  29. anonymous
    • one year ago
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    What do you mean?

  30. rational
    • one year ago
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    in the diagram the boat is approaching near to the light house, yes ?

  31. anonymous
    • one year ago
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    yes

  32. rational
    • one year ago
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    since the distance is decreasing, the velocity is negative

  33. rational
    • one year ago
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    the distance is decreasing at a rate of 36/5 km per hour is same as saying the distance is increasing at a rate of \(\color{red}{-}\)36/5 km per hour

  34. rational
    • one year ago
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    i have a debt of $100 is same as saying i have -$100

  35. anonymous
    • one year ago
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    Oh I see! Thanks lots!

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