Question

From where Kiana is standing, she must look up at a 50° angle to see the top of a building. If she backs up 50 feet, she will need to look up at a 40° angle to see the top of the same building. Approximately how tall is the building?

Answer 1

B. 141.8ft

Explanation:

Answer 2

For this case, what we must do is solve the following system of equations:
tan (50) = h / x
tan (40) = h / (x + 50)
Solving the system we have:
(x + 50) * tan (40) = h
(x) * tan (50) = h
Matching:
(x + 50) * tan (40) = (x) * tan (50)
Rewriting:
x (tan (50) - tan (40)) = 50 * tan (40)
x = 50 * tan (40) / (tan (50) - tan (40))
x = 118.9692621
Substituting:
h = (x) * tan (50)
h = (118.9692621) * tan (50)
h = 141.7820455
Answer:
The height of the building is:
h = 141.7820455 ft