Posted by **Samuel** on Monday, March 1, 2010 at 9:27pm.

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 -
**bobpursley**, Monday, March 1, 2010 at 9:46pm
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 -
**Nathan**, Monday, March 1, 2010 at 10:00pm
what do you mean by 1/(sqrt()?

- To:bobpursley -
**Nathan**, Monday, March 1, 2010 at 10:04pm
what do you mean by 1/(sqrt()?

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