## Fundamentals of Physics Extended (10th Edition)

$f_{s}$ decreases as $\theta$ and F increase.
Since the box is stationary, the forces on the box are equal and opposite. When $\theta$ and F increase, there is less resultant force pulling the box to the right. If there is less force to the right, then there has to be less force ($f_{s}$ ) pushing back in the opposite direction.