The angle between the resultant contact force and the normal force exerted by a body on the other is called the angle of friction. Show that it `lamda` be the angle of friction and `mu` the coefficient of static friction. `lamdaletan^-1mu`.

Explanation

To show that the angle of friction \( \lambda \) is less than or equal to \( \tan^{-1} \mu \), where \( \mu \) is the coefficient of static friction, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Forces**:
- Consider a block resting on a surface. The forces acting on the block include the normal force \( N \) acting perpendicular to the surface and the frictional force \( F \) acting parallel to the surface.

2. **Resultant Contact Force**:
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