
Jon S. answered 04/04/20
Patient and Knowledgeable Math and English Tutor
The distance from the top of the tree to your position (108 feet) forms the hypotenuse of the right triangle, while height of the tree to above you (above 5.75 feet) will be the side opposite the angle of elevation (66).
Using the sine function for the elevation angle (= opposite/hypotenuse):
sin(66) = height of tree above you/108 feet
108*sin(66) = height of tree above you
108*sin(66) + 5.75 = height of tree