Answer
The change in the angle of elevation when a 4% error occurs is less than 0.01 radians ($\approx0.57^\circ$) from $75^\circ$
Work Step by Step
The given height of the building is h and the distance from the point on the ground is 30 ft.
change in height(dh):
$\frac{dh}{h}$ is less than 4%
$\theta =75^\circ$ angle of elevation
so
$h=30\tan\theta$
so $\frac{dh}{h}=\frac{30\sec^2{\theta}d\theta}{30\tan\theta}$
$0.04\lt\frac{30\sec^2{75}d\theta}{30\tan75}$
$0.01\lt d\theta$
