Safety rules place a ladder's base 1 foot from the wall for every 4 feet of ladder length. What angle does the ladder make with the ground?

1. Let the base sit a feet from the wall, so the ladder measures 4a feet. 2. The side adjacent to the ground angle is a and the hypotenuse is 4a. 3. So cos of the angle equals a divided by 4a, which is 1/4. 4. The a cancels, so the answer holds for a ladder of any length. 5. The inverse cosine of 1/4 is about 75.5 degrees. 6. About 14.5 degrees is the complement, the angle the ladder makes with the wall rather than with the ground. _Source: OpenStax Algebra and Trigonometry (CC BY 4.0), Ch 9 "Trigonometric Identities and Equations", section 9.5 Solving Trigonometric Equations_