Re: Please show us your attempts (n/t)

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Posted by I. Newton on September 12, 2002 at 09:04:56:

In Reply to: Please show us your attempts (n/t) posted by Subhotosh Khan on September 11, 2002 at 17:03:38:

I created a right triangle to represent the problem with one leg equal to 600t and the other equal to 300-500t.

I then set the distance equal to the SQRT[ (600t)^2 + (300-500t)^2].

Next I took the derivative of this distance with respect to t, time.

1/2 * ( U )^-.5 * du
(.5(610,000t^2 - 300,000t + 90,000)^-.5 ) * ( 1,220,000t - 300,000)

I then solved for d/dt at .25 and got 43.5

Is this right??

: : Plane A is flying west at the rate of 600mph and a second plane B, 300 miles south of A, is flying north at the rate of 500 mph.

: : a) At what rate is the distance between the two planes changing after 15 minutes?
: : b) When do the planes cease to approach one another?

Follow Ups:

For part B... Subhotosh Khan 12:18:12 09/12/02 (0)
Looks OK to me .... Subhotosh Khan 12:01:03 09/12/02 (0)

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: I created a right triangle to represent the problem with one leg equal to 600t and the other equal to 300-500t. : I then set the distance equal to the SQRT[ (600t)^2 + (300-500t)^2]. : Next I took the derivative of this distance with respect to t, time. : 1/2 * ( U )^-.5 * du : (.5(610,000t^2 - 300,000t + 90,000)^-.5 ) * ( 1,220,000t - 300,000) : I then solved for d/dt at .25 and got 43.5 : Is this right?? : : : : Plane A is flying west at the rate of 600mph and a second plane B, 300 miles south of A, is flying north at the rate of 500 mph. : : : a) At what rate is the distance between the two planes changing after 15 minutes? : : : b) When do the planes cease to approach one another?

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