9514 1404 393
Answer:
24 feet
Step-by-step explanation:
The side adjacent to the angle is given, and the hypotenuse of the triangle is the unknown. The cosine relation applies:
Cos = Adjacent/Hypotenuse
hypotenuse = ladder length = (5 ft)/cos(78°) ≈ 24.0 ft
The ladder is about 24 feet long.
