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At noon, ship A is 20 nautical miles due west of ship B. Ship A is sailing west at 23 knots and ship B is sailing north at 17 knots. How fast (in knots) is the distance between the ships changing at 5 PM? (Note: 1 knot is a speed of 1 nautical mile per hour.)

  • Calculus -

    draw the diagram.

    I see this

    d= sqrt(ND^2+(WD+20)^2) where ND is north distance, WD is west distance
    take the derivative

    d'= 1/2 *1/(sqrt( ) * 2ND*ND'+2(WD+20)(WD')

    ND= 17kt/hr*5hrs ND'=17kts/hr
    WD=23*5 WD'=23

    have fun.

  • Calculus -

    what do you mean by 1/(sqrt()?

  • To:bobpursley -

    what do you mean by 1/(sqrt()?

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