Question

An observer stands 25 feet from the base of a 50 foot flagpole and watches a flag being lowered at a rate of 5 ft/sec. Determine the rare at which the angle of elevation from the observer to the flag is changing at the instant that the flag is 25 ft.

Keep getting like .1 or .2, help apreciated

Answer 1

elevation angle A = 45 degrees = pi/4 radians

tan A = h/25
d tan A/dA = sec^2 A = (1/25) dh/dA
so
25 sec^2 A * dA/dt= dh/dt = 5

dA/dt = (1/5) cos^2 A
but cos^2 A = 1/2
dA/dt = .1 radians/second
So I agrees
but maybe you want degrees?
.1 Rad/s( 180 deg/rad) = 18 degrees/second

Answer 2

oh its in radians

thanks a bunch, makes more sense :D

Answer 3

You are welcome ;)