A kite 100 ft above the ground moves horizontally at a speed of 5 ft/s. At what rate (in rad/s) is the angle (in radians) between the string and the horizontal decreasing when 200 ft of string have been let out?

Respuesta :

Answer: [tex]= 0.013 rads^{-1}[/tex]

Step-by-step explanation:

given data:

speed of kite = 5 ft/s

height of the kite = 100 ft above the ground.

decrease = 200 ft

Solution:

[tex]\frac{dy}{dx} = 5 ft/s\\\\\\[/tex]

 θ = [tex]arcsin \frac{100}{200}[/tex]

next we relate  θ and x with respect to time t.

[tex]\frac{x}{100} =[/tex] cot θ

[tex]0.01\frac{dx}{dt} =-csc^{2}[/tex] θ[tex]\frac{d}{dt}[/tex]

[tex]\frac{d}{dt} = \frac{0.01\frac{dx}{dt} }{-csc^{2} \frac{\pi }{6} }[/tex]

[tex]= \frac{0.01(5)}{-csc^{2}\frac{\pi}{6} }[/tex]

[tex]= \frac{0.05}{-2^{2} }[/tex]

[tex]= 0.013 rads^{-1}[/tex]