A plane flies horizontally at an altitude of 5 km
posted by yolana .
A plane flies horizontally at an altitude of 5 km and passes directly over a tracking telescope on the ground. When the angle of elevation is π/3, this angle is decreasing at a rate of π/4 rad/min. How fast is the plane traveling at that time? (Round your answer to two decimal places.)

Please stop posting your question on other people's work, If I did the same to you, Im sure you wouldnt like it.

Draw the triangle. h=5km, let x be the the horizontal distance.
Then angle of elevation=arctan h/x
tan angle=h/x
x= h ctn angle
dx/dt=h d ctnTheta/dt * dTheta/dt
so solve for dx/dt, you know dTheta/dt, and you can take the derivative of ctn 
a jet plane begins a steady climb at 17 degrees and flies 5 km measured along the ground. Wht is its change of altitude