Draw a right triangle to represent the problem. The vertical height of the triangle is 9 ft, and it represents the tree. The horizontal length, at the bottom of the tree is ground level and has a length of 13 ft.
Let x = angle of elevation.
By definition, tan x = 9/13 = 0.6923 x = arctan(0.6923) = 34.7 deg. = 35 deg (approx)
