Anton Calculus question

[markbenjamin]

Hi All. I am stumped by what must be a very simple trig differentiation question. Some kind of mental block.
A plane is flying horizontally at 3800 feet. It is heading towards a fixed point P on the ground at a constant altitude.
The angle of elevation of the plane is theta. The distance between the plane and the fixed point is s

When theta = 30 degree at what rate is the distance s between the plane and the point P changing in feet per degree?

I started by writing that sin theta = 3800/s
so s = 3800/sin 30 degrees
and s' = 3800* the differential of sin 30....but I get a change of hundreds of feet per degree. I am sure this is not so hard but I am totally stumped.
By the way the answer is 1.75 according to the key, I need to understand it though.

 

[pappus]

Hi All. I am stumped by what must be a very simple trig differentiation question. Some kind of mental block.
A plane is flying horizontally at 3800 feet. It is heading towards a fixed point P on the ground at a constant altitude. <-- if this word could be replaced by speed the question could be solved
The angle of elevation of the plane is theta. The distance between the plane and the fixed point is s <-- the distance per time depends on the velocity of the air-plane flying parallel to a plane

...

In my opinion the text of the question is incomplete.