Related Rates, find d(theta)/dt

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SUMMARY

The discussion focuses on calculating the rate of change of the angle θ (d(θ)/dt) as a plane approaches an observer from an altitude of 5 miles, with a horizontal distance change rate (dx/dt) of -600 mi/h. The correct approach involves using the relationship tan(θ) = height/distance, where the height remains constant at 5 miles. The formula derived for d(θ)/dt is based on the derivative of arctan(500/x), leading to the conclusion that the observer must consider the negative rate of change in distance as the plane approaches.

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kingdomof
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Homework Statement


A plane is approaching an observer from an altitude of 5 mi at a dx/dt of 600 mi/h. Find the d(theta)/dt when theta is 30 degrees, 60 degrees, and 75 degrees.


Homework Equations



tan(theta) = x/y
5csc(theta) = r

The Attempt at a Solution



For my d(theta)/dt I had the formula of 3000/(5csc(theta))^2

The answers I had were wrong according to the text.

Please help.
 
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kingdomof said:

Homework Statement


A plane is approaching an observer from an altitude of 5 mi at a dx/dt of 600 mi/h. Find the d(theta)/dt when theta is 30 degrees, 60 degrees, and 75 degrees.


Homework Equations



tan(theta) = x/y
5csc(theta) = r

The Attempt at a Solution



For my d(theta)/dt I had the formula of 3000/(5csc(theta))^2

The answers I had were wrong according to the text.

Please help.

You have too many variables. All you need are two: one for the horizontal distance and one for the angle.

I presume that y is the altitude of the plane, which is given and is not changing. I'm guessing that r is the length of the hypotenuse of the right triangle. Keep in mind that if x is the horizontal distance, it is decreasing because the plane is approaching the observer, so dx/dt will necessarily be negative.

I have no idea how you got what you have for d(theta)/dt.
 
All you need is tan(\theta)= height/distance. You are told that the height is always 5 mi and that the distance is decreasing at 600 mi/hr.

With \theta= arctan(500/x), what is d\theta/dx and from that what is d\theta/dt?
 

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