Question

(Trigonometry) A 25-foot ladder leans against a building. The ladder's base is 13.5 feet from the building. Find the angle which the ladder makes with the ground.

Answer 1

Here, in this situation, 
Hypotenuse = 25 feet
base = 13.5 feet

Now, Cos Ф = B / H
Cos Ф = 13.5 / 25
Cos Ф ≈ 1/2
Ф = Cos⁻¹(1/2)
Ф = 45  [ Cos 45 = 1/2 ]

In short, Your Answer would be approximately 45 degrees

Hope this helps!