Answer:
68 degrees
Explanation:
The ladder, the building and the ground together make up a right triangle with angle of elevation to be determined.
The side opposite this angle is 10 ft; the distance of the foot of the ladder from the building is 4 ft. Thus,
tan x = (opp side) / (adj side) = 10/4. Using the inverse tangent function, we find that the angle in question is
arctan (10/4) = 68 degrees