question is- A rocket is launched vertically and is tracked by a radar station located on the ground 5km from the launch pad. Suppose that the elevation angle θ of the line of sight to the rocket is increasing at 1° per second when θ = 30°. What is the velocity of the rocket at this instant?
I have tried the question out and have no idea on where to even begin! any help?
$$\tan\theta=\frac{h}{x}$$
Note that $x$ is a constant as it is distance of point where rocket took off from radar.
$$x=\dfrac{h}{\tan\theta}$$
Differentiate both sides wrt $t$ and use $dh/dt=v$
$$0=\tan\theta \dfrac{dh}{dt}-h\sec^2\theta\dfrac{d\theta}{dt}$$