Answer
5.8 ft
Work Step by Step
$\frac{opposite\,side}{adjacent\,side}=\tan \theta$
In this case,
opposite side$\rightarrow$ height of the post
adjacent side$\rightarrow$ length of the shadow
$\theta \rightarrow$ angle of elevation.
$\implies$ Height of the post=$\tan(\frac{151}{2})^{\circ}\times1.5\,ft=5.8\,ft$
