During an experiment on an adjustable rough incline, a student slowly increases the angle until a small crate that had been at rest just begins to slip. The critical angle at which motion starts is measured to be θ=28∘.
Assume the crate behaves as a particle, the contact surface is uniform, and air resistance is negligible.
a. Calculate the coefficient of static friction between the crate and the incline. Express your answer to two significant figures.