1. The problem statement, all variables and given/known data A coin of mass m is at rest on a book that has been tilted at an angle θ with the horizontal. By experimenting, you find that when θ is increased to 13o, the coin is on the verge of sliding down the book, which means that even a slight increase beyond 13o produces sliding. What is the coefficient of static friction μs between the coin and the book? 2. Relevant equations F=ma, f(static friction) = (μ)*normal force 3. The attempt at a solution I drew out the problem, but from here I am sort of lost.