Some difficult written task

A surveyor, standing 30 ft from the base of a building, measures the angle of elevation

to the top of the building to be 75. How accurately must the angle be measured for the

percentage error in estimating the height of the building to be less than 4%?

I am not sure where to even start on this.

Re: Some difficult written task

Start by expressing h as a function of the angle α: h = h(α). Let Δh = 0.04 ⋅ h(75°). We have approximately Δh = h'(75°) ⋅ Δα, from where we can find Δα.