E-5 Friction

As we change the incline angle, the component of gravitational force acting on the block is changing, hence the normal force changes. When the angle reaches a value so that the static frictional force is equal to the component of the gravitational force mg along the incline surface, i.e. mgsinq. Then we can calculate m_s = tanq. That doesn't mean that the coefficient of friction depends on q. The coefficient of friction depends only on the materials of the contact.