We have a triangle, when:
hypotenuse=slant height=20 ft
opposite side=height of the tree=?
angle formed by the tree with the ground=72º
sin Ф=opposite/ hypotenuse ⇒ opposite=(hypotenuse)(sin Ф)
In this case:
oppssite=20 ft /sin 72º=19.021...≈19
Answer: the heigth of the tree is 19 ft.
