Here, AB is the chimney, CD the observer and ∠ ADE the angle of elevation .
In this case, ADE is a triangle, right-angled at E and we are required to find the height of the chimney.
We have AB = AE + BE = AE + 1.5
and DE = CB = 28.5 m
To determine AE, we choose a trigonometric ratio, which involves both AE and DE.
Let us choose the tangent of the angle of elevation.
Now, tan 45° = AE / DE
i.e., 1 = AE / 28.5
AE = 28.5
So the height of the chimney (AB) = (28.5 + 1.5) m = 30 m.